Comp-Based Value Estimation
Comp-Based Value Estimation
Use recent comparable sales (closed within six months, within 0.5 mile) to validate whether you're paying a fair price. Compare on a price-per-unit or price-per-square-foot basis, and back-check the implied cap rate against the market.
Key takeaways
- Identify 3–5 comparable sales: similar property type, size, and quality, closed within the last six months
- Analyze on price-per-unit (multifamily), price-per-SF (office, retail, industrial), or cap rate basis
- A 5–10% premium is justified if the subject is newer or better-located; a 5–10% discount if older or weaker
- Back-calculate the implied cap rate: Price / Annual NOI. If it's materially tighter than market, you're overpaying.
- Sales data lags the market by 30–90 days, so validate against active listings and pending sales
Why compare sales (not listing prices)
Active listings are asking prices; closed sales are transaction prices. Sellers list at aspirational prices; buyers often negotiate down. Using closed sales data is more reliable than asking prices.
Similarly, pending sales (under contract) are often reported at offer price, which may not reflect the final negotiated price after inspections and appraisals.
Best practice: Use closed sales from the last 6 months. If the market is fast-moving, use last 3–4 months. If slow, expand to 9–12 months.
Sources for comparable sales data
MLS (Multiple Listing Service):
- Most comprehensive source. Realtor.com, Zillow, Redfin all pull from local MLS.
- Access requires a real estate license (or a broker/agent willing to share).
- Provides detailed sale price, sale date, property characteristics, days on market.
Zillow Zestimate:
- Shows property value estimates and recent sale prices for individual comps.
- Includes sale date and price history.
- Less detail than MLS, but publicly available.
CoStar (commercial):
- Gold standard for commercial property comps.
- Expensive ($5,000–20,000/year), but widely used by institutions.
- Provides detailed financial data and cap rate benchmarks.
LoopNet (commercial):
- LoopNet (owned by CoStar) is the commercial MLS equivalent.
- Many brokers list commercial deals here.
- Less comprehensive than CoStar but more transparent on pricing.
Tax assessor records:
- Public records. Search by county or municipality website.
- Provides sale price, sale date, property size, assessed value.
- Usually lags by 30–60 days but is comprehensive.
Broker opinion of value:
- Local commercial brokers can provide recent sales data and market analysis.
- Brokers are incentivized to provide accurate data (builds reputation for future deals).
- Usually free if you engage the broker.
Structuring the comp analysis
Build a sales comp table:
| Comp Address | Sale Date | Sale Price | Units | Price/Unit | Cap Rate | Adjustments | Adjusted Price/Unit | Notes |
|---|---|---|---|---|---|---|---|---|
| 111 Main St | Jan 2025 | $2,100,000 | 20 | $105,000 | 4.8% | None | $105,000 | 2010 const. |
| 222 Oak Ave | Feb 2025 | $2,250,000 | 20 | $112,500 | 4.6% | +5% (reno) | $106,875 | Renovated 2024 |
| 333 Pine Blvd | Dec 2024 | $1,950,000 | 18 | $108,333 | 5.0% | None | $108,333 | 1995 const. |
| Median | $107,403 |
Subject property (20 units): $107,403 × 20 = $2,148,060 as fair-market value.
If the asking price is $2,000,000, you're getting a 7% discount (buyer friendly). If asking is $2,300,000, you're paying an 8% premium (seller friendly).
Adjustments for property differences
Similar to rent comps, apply adjustments for age, condition, location, and amenities:
| Factor | Adjustment |
|---|---|
| Newer (0–5 years) vs. older (>20 years) | +5–10% |
| Major recent renovation vs. deferred maintenance | +5–15% |
| Prime location vs. secondary location | +5–15% |
| Higher occupancy and lower turnover vs. stabilized | +0–5% |
| More desirable amenities (parking, courtyard) vs. basic | +3–8% |
| Larger (economies of scale) vs. single unit | +0–3% |
Example: Comp sold for $100,000/unit. Comp was:
- 2005 construction (subject is 2015): −5% = $95,000
- Excellent condition (subject has deferred maintenance): −5% = $90,250
- Prime location (subject is one block away): −3% = $87,543
Adjusted value: $87,543/unit. For a 20-unit building, that's $1,750,860.
Back-checking with cap rate
After estimating value based on comps, back-check using cap rate:
Implied Cap Rate = Annual NOI / Purchase Price
If you're buying at $2,150,000 and NOI is $107,500 (based on market rents and expenses), implied cap rate is 5.0%.
Compare to recent market cap rates:
- If recent comps sold at 5.0–5.2% cap rates, your deal is at-market. ✓
- If recent comps sold at 5.5% cap rates, your deal at 5.0% is tight (you're overpaying, or the property is superior). ⚠
- If recent comps sold at 4.5% cap rates, your deal at 5.0% is a discount. ✓
How to calculate implied cap rate from comps:
- For each comp, divide the sale price by the comp's estimated NOI (at acquisition).
- Average the cap rates.
- Compare to your deal.
Comps and cap rates should converge:
- Comp 1: $2,100,000 / $100,000 NOI = 4.76% cap rate
- Comp 2: $2,250,000 / $105,000 NOI = 4.67% cap rate
- Comp 3: $1,950,000 / $97,500 NOI = 5.0% cap rate
- Average market cap rate: 4.81%
If you can buy the subject at a 5.0% cap rate, you're getting a fair deal (slightly wide of the 4.81% average, which is normal for properties with execution risk or less-known brokers).
Red flags in comp analysis
Flag 1: No recent sales. If you can only find sales from 12+ months ago, the market has moved. Rental rates may have changed, and cap rates may have expanded or compressed. Caveat emptor.
Flag 2: Outlier sales. If one comp sold at 4.0% cap rate while others are at 5.5%, the 4.0% comp either had off-market terms (owner financing, portfolio sale, distressed buyer) or was a trophy property. Discard outliers and use the middle range.
Flag 3: Distressed sales. Foreclosures, REO (bank-owned), and short sales often close at 10–20% discounts to market. Use them cautiously; they don't reflect fair-market value.
Flag 4: Portfolio sales. When one buyer acquires a portfolio of properties (e.g., 50 units across three buildings), the effective price/unit may be 5–10% below individual sales (volume discount). Adjust if you're buying a single property.
Comp selection by property type
Multifamily: Use recent sales of 10+ unit buildings (your property size ±30%). Small buildings (2–9 units) trade at premiums due to scarcity; large buildings (100+) at discounts due to institutional buyer concentration.
Office: Use recent sales of multi-tenant office in the same submarket. CBD (downtown) office trades at higher cap rates than suburban. Class A (modern, full-service) tighter cap rates than Class B (basic amenities) and Class C (older, limited services).
Retail: Challenging—retail is segmented by tenant type (grocery-anchored vs. strip center vs. high-street). Use comps of the same subtype. Net-lease groceries trade tighter cap rates (4–5%) than inline retail (5–7%).
Industrial: Modern logistics (0–10 years old) tighter cap rates (4–5%); older industrial warehouses (20+ years) wider cap rates (6–7%).
Adjusting for market timing
Cap rates move. A property that sold in 2021 at a 3.5% cap rate (pandemic low) cannot be directly compared to market sales in 2024 at 5.5% cap rates (higher rates). Adjust for the rate environment:
- Note the sale date and prevailing mortgage rate at that time.
- Estimate how cap rates have moved since (usually correlated with interest rate moves).
- Add or subtract basis points to bring the comp into 2024 pricing.
Example:
- Comp sold in March 2021: $2,000,000, NOI $70,000, 3.5% cap rate. Mortgage rates were ~2.8%.
- Current (2024): Mortgage rates are 6.5%, cap rates have widened by 200 bps to 5.5%.
- Adjusted comp value: $70,000 / 0.055 = $1,272,727.
- Or: $2,000,000 × (3.5% / 5.5%) = $1,272,727.
This is a rough adjustment; use broker opinion for precision.
When sales comps conflict with rent comps
Sometimes cap rate from sales comps doesn't match cap rate implied by rent comps:
- Sales comps suggest $2,000,000 (5.0% cap rate on $100,000 NOI).
- Rent comps suggest $1,800,000 (from market rents × expense assumptions × 5.5% cap rate).
Possible explanations:
- Market rent expectations differ. Rent comps are based on current market rent; buyers of older properties may expect rent growth. Investigate.
- Expense assumptions differ. If sales comps have lower expense assumptions (more optimistic), they imply higher NOI and thus higher value. Check expense benchmarks.
- Buyer profile differs. Institutional buyers (REITs, funds) are willing to buy at tighter cap rates (less return) due to lower cost of capital. Individual buyers need higher cap rates. Your buyer profile matters.
Resolution: Use the average of rent-based and sales-comp-based valuations, with more weight to recent sales (because they reflect actual transaction prices, not appraisals or estimates).
Building a value comp flowchart
Related concepts
Next
With market rent and value estimates validated, you're ready to summarize the analysis: the one-page property sheet that brings everything together into a final go/no-go decision.