Comparable sales analysis - commonly called "pulling comps" - is the foundation of accurate real estate valuation. Whether you are evaluating a fix and flip, a BRRRR deal, a rental property, or a wholesale opportunity, your entire analysis depends on knowing what the property is actually worth.
In this guide, we will cover how to find reliable comparable sales, how to adjust for differences between properties, and how to avoid the common mistakes that lead to inaccurate valuations.
What Are Comparable Sales?
Comparable sales (comps) are recently sold properties that are similar to the property you are evaluating. Appraisers, real estate agents, and investors all use comps to estimate market value. The principle is simple: a property is worth approximately what similar properties have recently sold for in the same area.
The Three Key Criteria for Good Comps
1. Location Proximity
The best comps are within 0.5 miles of your subject property, in the same neighborhood or subdivision. You can extend to 1 mile if necessary, but anything beyond that introduces too many location variables. Never cross major boundaries like highways, school districts, or significant changes in neighborhood character.
2. Recency of Sale
Comps should have sold within the last 90 days. In a fast-moving market, prioritize comps from the last 30-60 days. You can extend to 6 months if there are not enough recent sales, but adjust for market trends. In an appreciating market, older comps may understate current value.
3. Physical Similarity
Your comps should match the subject property as closely as possible on these attributes:
- Square footage (within 15-20%)
- Number of bedrooms and bathrooms
- Lot size (especially for suburban and rural properties)
- Property type (single-family, condo, townhome)
- Age and construction style
- Condition and level of updates
- Garage (attached vs detached, 1-car vs 2-car)
Where to Find Comparable Sales
- MLS (Multiple Listing Service): The gold standard. Requires access through a real estate agent or investor-friendly MLS subscription.
- County records: Public records show all recorded transactions. Free but often delayed and lack property details.
- Zillow/Redfin/Realtor.com: Good for a quick look, but data can be incomplete or outdated.
- Opsite: AI-powered comp analysis pulls recent sales, adjusts for property differences, and provides a weighted valuation estimate automatically.
How to Adjust Comps
No two properties are identical, so you need to adjust comp values to account for differences. The principle is straightforward: add value for features your subject property has that the comp does not, and subtract value for features the comp has that your subject lacks.
Common adjustments:
- Square footage: Typically $50-$150 per square foot difference, depending on market
- Bedrooms: $5,000-$15,000 per bedroom
- Bathrooms: $5,000-$10,000 per full bathroom
- Garage: $10,000-$25,000 for garage vs no garage
- Condition: Renovated vs original condition can represent 15-30% of value
- Pool: $10,000-$30,000 depending on market (less in cold climates)
- Lot size: Varies significantly by market
Calculating Your Valuation
After pulling and adjusting 3-6 comps, calculate a weighted average to determine your estimated value. Give more weight to comps that are more similar to your subject property, more recent, and closer in location.
For investment purposes, it is wise to be conservative with your valuation. Use the lower end of your comp range when calculating ARV for a flip, and the higher end when estimating a purchase price ceiling.
Red Flags in Comp Analysis
- Comps with unusually high or low sale prices (could be distressed sales, family transfers, or data errors)
- Properties that were on the market for an unusually long time
- Sales with seller concessions or buyer incentives that inflate the recorded price
- New construction comps used for existing property valuations
- Comps from different school districts or across significant geographic boundaries
The Bottom Line
Accurate comp analysis is the single most important skill in real estate investing. An overestimated ARV leads to overpaying for properties and losing money. An underestimated value means you pass on profitable deals. Take the time to pull quality comps, make thoughtful adjustments, and always err on the side of conservative valuations.