A comparative market analysis (CMA) is an estimate of a property's value built from the recent sale prices of similar nearby properties, adjusted for the differences between them and the place you are pricing. It is the informal cousin of an appraisal: a real estate agent usually prepares it, no license-bound report is filed, and it carries no weight with a lender, but it is the fastest read on what a property is actually worth right now.
In practice
You start by pulling three to six properties that sold in the last six months within roughly a mile, matching on bedrooms, bathrooms, square footage, and age. Say you are pricing a 1,500 square foot duplex and you find three recent sales: one at $310,000 for 1,450 square feet, one at $330,000 for 1,600 square feet, and one at $300,000 for 1,400 square feet. Raw, those average to $313,333. The point of a CMA is the adjustment, not the average.
You normalize to price per square foot first: $213.79, $206.25, and $214.29, which average to $211.44. Multiply by your 1,500 square feet and you land near $317,000. Then you nudge for the things square footage does not capture. The $330,000 comp had a renovated kitchen your duplex lacks, so you knock $8,000 off its weight; the $300,000 comp backs onto a highway, so you add some back. After those adjustments you settle on a supportable value around $315,000, with a defensible range of $308,000 to $322,000. That range, not a single number, is the real output.
Why it matters to a small landlord
A CMA is how you avoid overpaying before you ever order an appraisal, and it sets the purchase price that every downstream number depends on. Pay $25,000 over a supportable CMA and you have quietly lowered your cap rate and stretched your payback for the full hold. It also feeds the front end of your deal analysis, because an honest value estimate is what keeps a seller's asking price from masquerading as the market. The discipline that separates a useful CMA from a hopeful one is using closed sales, not active listings, and adjusting comp by comp instead of trusting a flat average.
A CMA sits next to a few terms worth holding together. It is not an appraisal, which is a licensed, lender-ordered opinion the bank will actually lend against, and it values the building rather than the income, so it is distinct from rent comps, which estimate what the place should rent for. Keep it separate too from the county's assessed value, a tax figure that often trails the market by years. Treat all four as different witnesses answering the same question, and weigh them accordingly.