Illinois exam glossary
Principle of substitution: compare the useful alternative
A lower price is useful only if the alternative delivers what the buyer needs. Two houses can look alike and offer different rights, locations or completion dates. Substitution asks whether a buyer could obtain a genuinely comparable benefit elsewhere, without a costly wait.
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The short answer
The principle of substitution says that an informed, prudent buyer generally will not pay more for a property than the cost of obtaining an equally desirable alternative without costly delay. It helps explain value in all three approaches: sales comparison, cost and income. Equivalent usefulness matters more than an identical appearance. Compare rights, location, condition, timing and risk before treating a cheaper property as a substitute.
This is a national valuation principle used in Illinois broker exam preparation, not a statutory price limit. PSI places valuation in national category III, which has eight of 100 scored broker questions across the whole category. No separate substitution-question count is promised. The examples illustrate reasoning and arithmetic, not an appraisal or a recommendation about a particular property.
Four checks before calling a property a substitute
- Start with the benefit and the date. Identify the property interest, use and effective date being considered. A market-value question concerns typical market participants, not an unexplained premium that only one particular purchaser would pay.
- Find a genuinely competing alternative. Compare legal rights, permitted use, location, physical usefulness, condition and the relevant buyer pool. Neither distance alone nor a matching floor plan proves that two properties compete.
- Compare timing and burdens on a consistent basis. A ready-to-use building and a construction proposal may deliver their benefits at different times and with different risks. Distinguish a buyer's total-cost comparison from an appraisal adjustment: do not simply add every buyer expense to market value.
- Use evidence, not a shortcut. Sales comparison analyzes competitive sales; cost analysis considers a substitute site and improvement; income analysis compares expected benefits and risk. Support adjustments and reconcile the available evidence. Do not turn the cheapest listing, one sale or a construction quote into an automatic final value. Do not choose a comparable merely because it supports a desired number.
| Approach | Alternative being compared | Main caution |
|---|---|---|
| Sales comparison | Other properties competing for the same buyers | Analyze rights, terms, condition, location and market conditions; nearest or newest does not automatically win |
| Cost | A suitable site and an improvement offering equivalent utility | A contractor's building quote alone omits the site and may omit other costs and timing; account for the stated improvement depreciation |
| Income | Other opportunities delivering comparable expected benefits and risk | Similar initial income does not prove equal durability, capital needs or value |
| All three | A credible alternative at the relevant date | Supporting all three approaches does not require developing all three in every assignment |
The distinctions that matter
| Distinction | How it works | What to notice |
|---|---|---|
| Substitution and the cheapest property | Substitution compares equivalent benefits and availability. A lower-priced property with inferior rights, major repair needs or a costly delay is a different package. | Ask what the price actually buys. |
| A substitute and a duplicate | Competitive usefulness does not require identical construction. Relevant physical and legal differences still need analysis. | Matching appearance is neither necessary nor sufficient. |
| Substitution and conformity | Substitution asks what else a purchaser could choose. Conformity concerns a property's relationship to compatible surroundings. | Alternative choice and neighborhood fit are different ideas. |
| Substitution and contribution | Substitution compares alternatives. Contribution asks what a component adds to the whole property's value. | A feature's construction bill is not automatically its value adjustment. |
| Substitution and competition | Substitution describes the comparison among alternatives. Competition concerns market participants and supply responding to opportunities and demand. | A buyer switching properties and developers entering a profitable market illustrate different principles. |
| Replacement and reproduction | Replacement aims at equivalent usefulness with a modern design. Reproduction aims at a replica using the same or similar design and materials. | An obsolete layout need not be copied merely to provide equal utility. |
| Price and market value | An asking price, an offer and a completed transaction price describe different evidence. A market-value opinion follows its stated definition, date and supported analysis. | A listing or a buyer-specific premium does not alone establish market value. |
Work through the facts
1. A premium with no stated benefit
For an exercise, assume two properties can actually be acquired now on equivalent terms. They offer equivalent rights, location, condition and utility. One costs $520,000 and the other $495,000; no additional benefit explains the difference.
- $520,000 - $495,000 = $25,000.
- The less expensive alternative supplies the same stipulated benefit without delay.
Answer: Substitution puts pressure on the unexplained $25,000 premium. It does not force a seller to accept $495,000 or make one offer a completed appraisal.
2. Nearby is not necessarily competing
A sale one block away has a legally different permitted use and serves another buyer group. A sale three miles away competes for the same users and offers similar relevant rights and utility.
- The nearby sale is not made equivalent by distance alone.
- The farther sale still needs location and other relevant analysis.
Answer: Investigate the genuinely competitive sale. Do not adopt an automatic one-mile rule or ignore the remaining differences.
3. Adjust the comparable using market evidence
A comparable sold for $330,000 without a garage. The subject has a garage. For this exercise, market evidence supports a $12,000 contribution for that difference, although building the garage would cost $25,000. All other differences have been addressed.
- Adjust the comparable upward for its inferior garage feature.
- $330,000 + $12,000 = $342,000.
- The $25,000 construction quote does not replace the stipulated market reaction.
Answer: The adjusted comparable indicates $342,000 on the stated facts. It is one indication, not a mandatory final opinion from a single sale.
4. The basic cost-approach calculation
An exercise supplies site value of $80,000, replacement cost new of improvements of $300,000 and total accrued improvement depreciation of $40,000. Assume the stated inputs are complete and appropriate.
- $300,000 - $40,000 = $260,000 for the depreciated improvements.
- Add the $80,000 site: $340,000.
- The stated improvement depreciation is not also subtracted from the site.
Answer: The cost-approach indication is $340,000. This simplified problem does not show that every real project's costs or every land-value change have been analyzed.
5. A delayed building is a different alternative
An existing building is usable now. A seemingly cheaper new substitute needs approvals and construction before it can be used. The facts give no quantified costs for delay, interim premises or completion risk.
- The no-costly-delay assumption has not been established.
- A bare construction quote is not a complete, immediately available substitute.
Answer: Analyze the missing time and risk facts. There is not enough information to calculate a justified premium or choose a final value.
6. The older sale fits the market better
A ten-month-old sale competes for the subject's buyers and closely matches its utility. A one-month-old luxury renovation serves a different segment.
- Recency is useful, but comparability also matters.
- The older sale must still be analyzed for market conditions and other differences.
Answer: The older sale may be more informative. Do not declare either sale best solely from its age or automatically add a time adjustment without evidence.
7. Similar income, different investment packages
Two properties each have stated annual NOI of $100,000. Market-supported illustrative capitalization rates, reflecting the stated differences in risk and expected benefits, are 8% and 10%.
- $100,000 / 0.08 = $1,250,000.
- $100,000 / 0.10 = $1,000,000.
- Equal initial NOI does not establish equivalent risk or equal value.
Answer: The indications differ by $250,000. Neither the lower price nor the higher capitalization rate alone identifies the better investment. These are supplied teaching rates, not current Illinois market rates.
8. A one-buyer benefit
Only an adjoining owner obtains a stated special operational benefit from acquiring the parcel. Other buyers do not receive that same benefit.
- The alternatives must be compared against the relevant value definition.
- A particular buyer's extra benefit is not automatically a benefit available to typical market participants.
Answer: Investigate the premium and market evidence instead of treating that one buyer's price as conclusive market value. Do not assume every assemblage premium is either wholly personal or always excluded.
Mistakes to avoid
- Choosing the cheapest address. First establish equivalent rights, benefit, timing and risk.
- Saying only one approach uses substitution. The principle supports sales comparison, cost and income.
- Calling an asking price market value. Listings can inform available competition, but asking prices are not completed sales or a value conclusion by themselves.
- Using a feature's cost as the adjustment. Analyze market contribution; an adjustment needs support.
- Forgetting the site or subtracting depreciation twice. Use the supplied components consistently and avoid counting the same loss twice.
- Invoking a rigid price ceiling. The principle is a market relationship under assumptions, not a law compelling a particular sale price.
Check your understanding
These are original teaching questions, not recalled or predicted PSI questions. Answer first, then explain why the other choices fail.
1. Which principle explains why a buyer compares a property with an equally desirable alternative available without costly delay?
- Mortgage amortization
- Substitution
- Conformity
- Adverse possession
Show answer and explanation
Answer: B. Substitution
Substitution concerns the competing alternative. Conformity concerns the surroundings; amortization is loan repayment, and adverse possession concerns a different property-rights issue. If the question concerned a component's added value instead, contribution would be relevant.
2. Which statement about substitution and the valuation approaches is correct?
- It requires every assignment to develop all three approaches
- It supports only the cost approach
- It underlies sales comparison, cost and income
- It supports only sales comparison
Show answer and explanation
Answer: C. It underlies sales comparison, cost and income
Substitution supports each approach through comparison of alternative properties, construction or expected benefits. Neither one-approach-only answer is complete. Supporting all three does not make all three mandatory in every assignment; the relevant scope and evidence still matter.
3. A nearby property has materially different permitted uses and buyers. What does its location alone establish?
- It is automatically the best comparable
- It must have the same market value
- Its legal differences can be ignored
- Proximity alone does not establish that it is a competitive substitute
Show answer and explanation
Answer: D. Proximity alone does not establish that it is a competitive substitute
The rights, use and buyer group must be analyzed. Nearness alone establishes none of the three automatic conclusions. A farther sale can be informative when it competes for the relevant buyers, but it still needs location analysis.
4. A comparable sold for $330,000 without the subject's garage. The supplied market contribution is $12,000; the construction quote is $25,000. What is the indicated adjusted sale price if all other differences are addressed?
- $355,000
- $342,000
- $330,000
- $318,000
Show answer and explanation
Answer: B. $342,000
Add the supported $12,000 to the inferior comparable: $342,000. Subtracting reverses the direction; adding $25,000 substitutes a construction quote for the given market reaction, while leaving the price unchanged ignores a stated difference. Different supported market evidence could change the adjustment.
5. Site value is $80,000, replacement cost new is $300,000 and total improvement depreciation is $40,000. What is the simplified cost indication?
- $300,000
- $260,000
- $340,000
- $380,000
Show answer and explanation
Answer: C. $340,000
The stated calculation is $80,000 + $300,000 - $40,000 = $340,000. The first choice omits depreciation, $260,000 omits the site, and $300,000 is only the new-improvement input. These complete stipulated inputs are not a universal checklist for every assignment.
6. What is the clearest distinction between replacement cost and reproduction cost?
- Reproduction ignores design and materials
- They both require an exact historic replica
- Replacement always means a higher final market value
- Replacement concerns equivalent utility; reproduction concerns a replica
Show answer and explanation
Answer: D. Replacement concerns equivalent utility; reproduction concerns a replica
Replacement focuses on a modern equivalent; reproduction focuses on replicating the improvement using the same or similar design and materials. Neither term alone establishes final market value. A different assignment purpose can affect which cost concept is appropriate.
7. An apparent new substitute is cheaper but cannot be used until construction and approvals are complete. The delay costs are unknown. What can you conclude?
- The cheaper quote conclusively sets current value
- The existing building can command any premium
- The timing difference needs analysis before treating the alternatives as equivalent
- A fixed 10% delay allowance applies everywhere
Show answer and explanation
Answer: C. The timing difference needs analysis before treating the alternatives as equivalent
The no-costly-delay assumption has not been established. Neither an unlimited premium nor a universal percentage follows, and the bare quote is incomplete. Quantified, relevant evidence would be needed before calculating the effect.
8. Two investments have annual NOI of $100,000. Use the stipulated 8% and 10% rates. Which pair of direct-capitalization indications is correct?
- $1,000,000 and $1,250,000
- $100,000 for both
- $1,250,000 and $1,000,000
- $800,000 and $1,000,000
Show answer and explanation
Answer: C. $1,250,000 and $1,000,000
Dividing the same annual NOI by 0.08 and 0.10 gives $1,250,000 and $1,000,000. The other pairs miscalculate, reverse the order or confuse income with value. Equal starting income does not prove equal risk, and the rates are supplied assumptions rather than current market advice.
9. A student says a $25,000 improvement must add $25,000 to value. Which distinction addresses the error?
- Contribution depends on the benefit to the whole, not automatically on the bill
- A mortgage balance always equals value
- All improvements have zero contribution
- A listing price proves the contribution
Show answer and explanation
Answer: A. Contribution depends on the benefit to the whole, not automatically on the bill
Contribution concerns the feature's effect on the whole property. Neither the bill nor a listing alone proves that effect. Zero is not a universal answer, and mortgage balance answers another question. Market evidence supporting the full cost could produce a different, justified amount.
10. What does substitution establish when the only evidence is a seller's asking price for a nearby house?
- The sale date of the subject is known
- The listing may inform competition, but it alone does not establish final market value
- The subject must sell for that exact price
- A completed comparable sale already exists
Show answer and explanation
Answer: B. The listing may inform competition, but it alone does not establish final market value
A listing can help identify alternatives; it is not a completed sale or a final market-value opinion by itself. The exact-price, completed-sale and known-date conclusions invent facts. Verified transactions and broader market analysis can add relevant evidence.
Common questions
What is the principle of substitution in real estate?
It explains how available alternatives influence value. An informed buyer generally will not pay more for a property than obtaining an equally desirable alternative without costly delay. First establish what rights and benefits the alternative provides and when they are available. A merely cheaper property is not necessarily equivalent.
Which appraisal approach is based on substitution?
All three approaches draw on it. Sales comparison considers competitive properties; cost considers creating an equivalent substitute; income considers alternative expected benefits and risk. A question about building a substitute points specifically toward the cost approach, but it would be wrong to conclude that the principle belongs only to that approach.
Must substitute properties be identical?
No. They need to compete in a meaningful way for the relevant participants. Rights, lawful use, location, condition, design and timing can matter even when two buildings look similar. Material differences need analysis rather than an assumption that either perfect identity or simple proximity is required.
Does substitution create a legal maximum selling price?
No. It expresses a market relationship under assumptions, rather than a law compelling a sale at a particular price. Delay, risk or different utility can make a supposed substitute less comparable. A particular buyer may also have a special benefit that needs separate analysis. That does not automatically establish the extra amount as market value or justify an unlimited premium.
Why can the closest or most recent sale be a poor comparable?
It may serve different buyers or offer materially different rights or utility. An older competitive sale can be informative, with market conditions and other differences analyzed. Fannie Mae's cited comparable-selection guidance illustrates this distinction within its program. Do not infer that distance, age or a fixed adjustment percentage alone settles the choice.
How do you adjust a comparable sale?
Analyze what its price indicates when relevant differences from the subject are addressed. In a simple exam exercise, a comparable lacking a beneficial feature gets the supplied positive adjustment; a superior comparable gets the supplied negative adjustment. Actual amounts require market support. A feature's cost and its contribution need not match.
How does the cost approach use substitution?
It considers a site and improvement supplying comparable usefulness. In a basic exam calculation, site value is added to replacement or reproduction cost new of the improvements, less the specified improvement depreciation. Construction timing, complete cost inputs and evidence still matter. Cost does not automatically equal market value.
What is the difference between replacement and reproduction?
Replacement concerns a modern improvement with equivalent usefulness. Reproduction concerns recreating the improvement using the same or similar design and materials. A modern substitute can avoid an obsolete layout instead of copying it. Do not assume that changing the cost basis also permits counting the same functional loss again without analysis.
How do income and risk affect substitution?
The initial income amount is only part of the package. Expected durability, vacancy, expenses, capital needs and other relevant risks can differ. A lower purchase price or higher capitalization rate does not by itself identify the better investment. The numerical examples use supplied assumptions, not live Illinois rental-market rates.
How is substitution different from conformity, contribution and competition?
Substitution compares alternatives. Conformity concerns fit with compatible surroundings. Contribution concerns what a component adds to the whole property. Competition concerns market participation and supply responding to demand and opportunities. The same property can illustrate several principles, so identify what the question actually asks.
Can a listing price or special buyer premium establish market value?
Not by itself. Listings can show offered competition, while a particular buyer may obtain a benefit that other participants do not receive. A market-value opinion follows its definition, effective date and evidence. The cited federal definition assumes typical motivation, informed parties and ordinary market conditions; it is not a rule that every recorded transaction price must equal market value.
Does every appraisal need all three approaches?
No. A principle underlying all three is different from a requirement to develop every approach in every assignment. Relevant methods depend on the property, evidence, assignment and applicable standards or program requirements. Fannie Mae guidance is a named lending-program example, not a universal Illinois exam rule or a substitute for the appraiser's applicable requirements.
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Official sources and scope
IAAO supplies the valuation vocabulary. Fannie Mae supplies named lending-program examples, not universal Illinois law; its cited pages direct UAD 3.6 users to a separate policy supplement. The federal provision illustrates a stated market-value definition. The worked figures are original assumptions, not current property values, market adjustment rates or a completed appraisal.
- PSI June 24, 2026: national Valuation outline
- IAAO Glossary, third edition: substitution and related valuation definitions
- Fannie Mae B4-1.3-08: competing properties and market area
- Fannie Mae B4-1.3-10: substitute construction and income context
- Fannie Mae B4-1.3-09: market-supported comparable adjustments
- 12 CFR 34.42(h): federal market-value assumptions
This is exam preparation, not advice for a specific transaction. State law and the applicable facts control. Our editorial and corrections process explains how to report an issue.