Running comps means finding recently sold properties similar to the one you're evaluating and using their sale prices, adjusted for differences, to estimate what your property is worth now or what it could sell for after repairs. It's one of the most important skills in real estate investing because almost every other number in your deal — your offer, your rehab budget, your expected rent — depends on getting this estimate right.
What Running Comps Means and Why It Matters
A "comp" (short for comparable sale) is a property similar to yours that has recently sold. Running comps means pulling a handful of these sales and using them to estimate the current market value of a property, or its ARV — what it would be worth after a renovation is complete.
This matters because comps are the foundation under almost every decision you make on a deal. Your maximum offer, your rehab budget, your expected resale price, and even your projected rent all trace back to a value estimate built on comps. Get the comps wrong and every number downstream is wrong too, no matter how precise your spreadsheet looks.
How to Find Comparable Sales: Step by Step
Good comps share as many physical and locational traits with your subject property as possible, and they sold recently enough to reflect current market conditions. In practice, that means working through a short checklist every time.
- •Pull sales from the last three to six months when possible; older sales may not reflect today's market.
- •Stay close geographically — ideally the same neighborhood or a tight radius, since location drives value more than almost anything else.
- •Match property type: single-family to single-family, condo to condo, not across types.
- •Match size within a reasonable range (square footage, bed/bath count, lot size).
- •Match condition and finish level as closely as you can; a fully renovated comp isn't a fair match for a property that needs work.
- •Use actual closed sales, not active listings — listings reflect what a seller hopes to get, not what a buyer actually paid.
- •Pull comps from multiple sources where you can: MLS data, county recorder records, and public sales databases, to cross-check each other.
How to Adjust Comps for Differences
No two properties are identical, so once you have a handful of solid comps, the next step is adjusting for the differences that remain. If a comp has an extra bedroom, an updated kitchen, a garage, or a larger lot, that difference has value — and you account for it by adding to or subtracting from that comp's sale price before using it in your average.
This is part math and part judgment. Professional appraisers follow formal adjustment guidelines and document every line item. As an investor, you don't need that level of formality, but you do need to be honest with yourself about which differences are significant and which ones are cosmetic. A rough rehab estimate for bringing a comp's finishes up (or down) to match your subject property is often a useful way to think about the adjustment.
Comps for Flips vs. Comps for Rentals
The comps you pull and how you use them shift depending on your exit strategy. A flipper is solving for resale value after repairs; a buy-and-hold investor is solving for current value and achievable rent. Both still rely on comps, just applied differently.
Flippers typically lean on comps to estimate ARV, then work backward using something like the 70% rule or a related max-offer rule to set a ceiling on what they can pay. Rental buyers use comps to sanity-check purchase price, then layer in rent comps and screens like the 1% rule or cap rate to judge cash flow potential.
| Factor | Comps for Flips (ARV) | Comps for Rentals (Value & Rent) |
|---|---|---|
| Primary goal | Estimate resale value after renovation | Estimate current value and achievable rent |
| Comp condition match | Match to a fully renovated finish level | Match to current, as-is condition |
| Time frame | Most recent closed sales, last 3-6 months | Recent sales plus active rent comps nearby |
| Common rules of thumb | 70% rule, max-offer rule | 1% rule, cap rate, cash flow |
| Biggest risk if wrong | Overpaying relative to a thin renovated margin | Overestimating rent or underestimating expenses |
Common Mistakes When Running Comps
Most comp errors come from shortcuts taken under time pressure, not from a lack of knowledge. Watch for these.
- •Using active listings instead of closed sales, which inflates the estimate.
- •Pulling comps from too wide a radius or across different submarkets.
- •Ignoring condition differences between a distressed subject property and renovated comps.
- •Relying on only one or two comps instead of a broader, consistent set.
- •Using stale comps in a market that's moved meaningfully since they closed.
- •Comparing across property types, like a townhouse to a detached single-family home.
Practical Takeaway
Running comps is a skill you build with repetition, not a formula you memorize once. Pull real closed sales, stay disciplined about location and condition matches, adjust honestly for the differences that remain, and then run your value estimate through whichever rule of thumb fits your exit strategy. Doing this consistently, deal after deal, is what separates an offer grounded in real data from a guess.
For a deeper walkthrough of turning comps into a full valuation, see our step-by-step ARV analysis guide, and pair your comps with solid local research before you commit to any market.
Frequently asked questions
How many comps do I need to run on a property?
Three to six solid, closely matched comps is a reasonable working minimum. In areas with more varied housing stock, you may need more comps to get a confident, consistent range.
How far back should comps go?
Aim for sales within the last three to six months whenever possible, since older sales may not reflect current market conditions. In slower markets with fewer transactions, you may need to go back further, but weight recent sales more heavily.
What's the difference between running comps myself and getting an appraisal?
A licensed appraiser follows formal, documented adjustment standards and produces a report lenders rely on. Investor comps are typically a faster, rougher version of the same process, useful for deciding whether to pursue a deal before paying for a formal appraisal.
Can I run comps without access to the MLS?
Yes. County recorder records, public sales databases, and various online tools can surface closed sales, though MLS access generally gives more detail on condition and features, which makes adjustments more accurate.
How this post was made: the figures above come from OnOffDeals’ own market-scan data (refreshed roughly monthly); the draft was written with AI assistance and checked against that data before publishing. Everything here is an estimate to help screen deals, not financial advice.
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