How to Find and Use Comparable Sales (Comps) for Real Estate Investing

Accurate property valuation is the foundation of every successful real estate investment. Whether you're analyzing a potential flip, evaluating a rental property, or making an offer on a wholesale deal, understanding how to find and use comparable sales (comps) is non-negotiable.

Get your comps wrong, and you might overpay by $30,000—or miss out on a great deal because you undervalued it. Get them right, and you'll negotiate with confidence, make data-backed offers, and consistently hit your profit targets.

This comprehensive guide will show you exactly how to find reliable comparable sales and use them to make smarter investment decisions.

What Are Comparable Sales (Comps) in Real Estate?

Comparable sales—commonly called "comps"—are recently sold properties that share similar characteristics with the subject property you're evaluating. Real estate investors, appraisers, and agents use comps to estimate what a property is worth based on actual market transactions.

The core principle is simple: if a similar house down the street sold for $250,000 last month, your property should be worth approximately the same amount, adjusted for differences.

Key characteristics that define comparable properties:

• Location: Ideally within 0.5 miles, same neighborhood or school district
• Property type: Single-family, condo, townhouse, multi-family
• Size: Square footage within 10-20% of subject property
• Bedrooms and bathrooms: Same or similar configuration
• Age and condition: Built within 10-15 years of each other
• Lot size: Similar land area for single-family homes
• Sale date: Sold within the last 3-6 months (fresher is better)

The more similar your comps are to your subject property, the more accurate your valuation will be.

Why Comps Matter for Different Investment Strategies

Different real estate strategies rely on comps in distinct ways:

House Flipping

For flippers, comps determine your After Repair Value (ARV)—what the property will sell for after renovations. Your entire profit calculation depends on this number. If your ARV is $300,000 but the property actually sells for $270,000, your expected $40,000 profit becomes a $10,000 profit (or worse).

Rental Properties

Rental investors use comps for two purposes: determining purchase price (using sold comps) and estimating rental income (using rental comps). You need both to calculate critical metrics like cap rate and cash-on-cash return.

Wholesale Deals

Wholesalers use comps to determine what an end buyer (usually a flipper) would pay, then work backward to calculate their assignment fee and offer price to the seller. Your comp accuracy directly impacts whether your deal gets accepted by a buyer.

Where to Find Comparable Sales Data

Access to quality comp data has improved dramatically over the past decade. Here are the best sources, from most accessible to professional-grade:

MLS (Multiple Listing Service)

Access level: Requires real estate agent or paid MLS access

The MLS is the gold standard for comp data. It provides:

• Complete sold property histories
• Listing photos showing condition
• Days on market and listing price history
• Detailed property features
• Agent remarks about condition and upgrades

If you're serious about investing, cultivate a relationship with an investor-friendly agent who can pull comps for you regularly. Some areas also offer MLS access through paid platforms like MRED or Flexmls.

Zillow

Access level: Free, publicly available

Zillow allows you to search recently sold properties and filter by:

• Sale date
• Price range
• Beds/baths
• Square footage

Pros: Quick, visual, includes property photos Cons: Data may be 30-90 days delayed; limited detail on condition; sometimes includes non-arm's-length sales

Zillow's "Zestimate" is NOT a reliable substitute for running proper comps—use it only as a starting point.

Realtor.com

Access level: Free, publicly available

Similar to Zillow but often includes MLS data more directly. The interface is less user-friendly, but data tends to be slightly more current in some markets.

Redfin

Access level: Free, publicly available

Redfin offers solid sold data with good photo archives. Their "Redfin Estimate" is slightly more reliable than Zillow's Zestimate but should still be verified with your own comp analysis.

County Assessor Records

Access level: Free, publicly available

Most county tax assessor websites provide:

• Sales history with dates and prices
• Property characteristics (square footage, bed/bath count)
• Tax assessment values
• Lot size and building details

Limitations: Photos are rare; condition information is minimal; sale dates may lag by months.

PropStream, DataTree, and BatchLeads

Access level: Paid subscription ($100-300+/month)

These investor-focused platforms aggregate data from multiple sources and offer:

• Advanced filtering options
• Property photos and condition indicators
• Owner contact information
• Foreclosure and distressed property flags

Useful for active investors running dozens of deals, but expensive for occasional use.

Professional Appraisals

Access level: $300-500 per property

Hiring a licensed appraiser gives you a detailed comparable market analysis with professionally selected comps. This is valuable for:

• Securing financing (lender-required)
• High-value properties where accuracy is critical
• Legal disputes or partnership disagreements

Most investors only order appraisals when required by lenders, relying on their own comp analysis for initial deal evaluation.

Step-by-Step: How to Pull Comparable Sales

Let's walk through the exact process to find and select comps for your subject property.

Step 1: Define Your Subject Property Criteria

Start by documenting the key characteristics of the property you're analyzing:

• Address and neighborhood
• Square footage: 1,850 sq ft
• Bedrooms/bathrooms: 3 bed / 2 bath
• Year built: 1985
• Lot size: 0.25 acres
• Garage: 2-car attached
• Condition: Needs moderate renovation
• Style: Ranch, brick exterior

Step 2: Set Your Search Parameters

Begin with tight parameters, then expand if needed:

Initial search criteria:

• Radius: 0.5 miles (or same neighborhood/subdivision)
• Sale date: Last 3 months
• Square footage: 1,665-2,035 sq ft (10% variance)
• Bedrooms: 3 (exact match)
• Bathrooms: 2 (exact match)
• Property type: Single-family residential

If you find fewer than 3-5 comps, expand gradually:

• Increase radius to 1 mile
• Extend sale date to 6 months
• Allow square footage variance to 20%
• Consider properties with 2-4 bedrooms

Step 3: Filter Your Results

Review each potential comp and eliminate:

• Non-arm's length sales: Family transfers, estate sales, foreclosures (unless your subject is also distressed)
• Outliers: Properties that sold unusually high or low (check listing history for explanations)
• Different conditions: A renovated comp isn't comparable to a fixer-upper without adjustments
• Significantly different features: Pools, basements, extra garages (or adjust for these)

You want 3-6 strong comps that closely match your subject property.

Step 4: Document Each Comp

Create a spreadsheet with these columns:

| Address | Sale Date | Price | $/Sq Ft | Sq Ft | Bed/Bath | Lot Size | DOM | Condition | |---------|-----------|-------|---------|-------|----------|----------|-----|-----------| | 123 Oak | 01/15/26 | $248K | $135 | 1,840 | 3/2 | 0.23 ac | 18 | Good | | 456 Elm | 12/28/25 | $242K | $133 | 1,820 | 3/2 | 0.28 ac | 31 | Average | | 789 Maple | 01/08/26 | $255K | $136 | 1,875 | 3/2 | 0.22 ac | 12 | Updated |

Include notes about special features: new roof, finished basement, corner lot, busy street, etc.

How to Adjust Comparable Sales for Accuracy

Raw comp prices are just the starting point. To get an accurate value, you must adjust each comp based on how it differs from your subject property.

The Basics of Comp Adjustments

If a comp has a feature your subject property lacks, subtract value from the comp's sale price.

If a comp lacks a feature your subject property has, add value to the comp's sale price.

Example: Your subject property has a 2-car garage. Comp #1 has a 3-car garage (worth ~$15,000 extra). Comp #1 sold for $260,000, so adjusted value is $260,000 - $15,000 = $245,000.

Common Adjustment Factors

Here are typical adjustments (values vary by market—these are examples):

Size differences:

• Square footage: $50-100 per sq ft difference
• Garage bays: $10,000-20,000 per bay
• Basement (finished): $30-50 per sq ft
• Additional bedroom: $5,000-15,000
• Additional bathroom: $8,000-20,000

Condition adjustments:

• Updated kitchen: +$15,000-30,000
• New roof: +$8,000-15,000
• Renovated bathrooms: +$5,000-12,000 each
• New HVAC: +$5,000-8,000
• Hardwood vs. carpet: +$3,000-8,000

Location factors:

• Corner lot: +$2,000-5,000
• Busy street: -$5,000-15,000
• Cul-de-sac: +$3,000-8,000
• Pool: +$5,000-20,000 (climate dependent)

Time adjustments:

• If market is appreciating 6% annually, add 0.5% for each month older than 3 months
• In declining markets, subtract accordingly

Creating an Adjusted Comp Table

Let's adjust three comps for a subject property (1,850 sq ft, 3/2, needs updates):

Comp #1:

• Sold: $248,000
• Size: 1,840 sq ft (10 sq ft smaller) = +$800
• Condition: Move-in ready (+$20,000 vs. subject's fixer condition)
• Adjusted value: $248,000 + $800 - $20,000 = $228,800

Comp #2:

• Sold: $242,000
• Size: 1,820 sq ft (30 sq ft smaller) = +$2,400
• Condition: Similar (no adjustment)
• Location: Corner lot (+$3,000 vs. subject's mid-block)
• Adjusted value: $242,000 + $2,400 - $3,000 = $241,400

Comp #3:

• Sold: $255,000
• Size: 1,875 sq ft (25 sq ft larger) = -$2,000
• Condition: Fully updated (+$25,000 vs. subject)
• Adjusted value: $255,000 - $2,000 - $25,000 = $228,000

Average adjusted value: ($228,800 + $241,400 + $228,000) / 3 = $232,733

Based on these comps, the subject property in its current condition is worth approximately $230,000-235,000.

Using Comps for ARV (After Repair Value)

For house flippers, ARV is your North Star. Here's how to use comps to calculate it accurately.

Find Comps That Match Your FINISHED Condition

When pulling comps for ARV, look for properties that represent what your subject will look like after renovations:

• Updated kitchens and bathrooms
• Modern finishes
• Good overall condition
• Sold recently (within 3-6 months)

You're essentially answering: "What do renovated homes in this area sell for?"

The ARV Formula

Step 1: Find 3-5 recently sold, updated properties Step 2: Calculate average price per square foot Step 3: Multiply by your subject property's square footage Step 4: Add/subtract for significant differences

Example:

• Comp #1: $285,000 / 1,920 sq ft = $148/sq ft (updated)
• Comp #2: $278,000 / 1,850 sq ft = $150/sq ft (updated)
• Comp #3: $292,000 / 1,950 sq ft = $150/sq ft (updated)
• Average: $149/sq ft

Your subject property: 1,850 sq ft x $149 = $275,650 ARV

The 70% Rule and Comps

The classic fix-and-flip rule states: Maximum offer = (ARV × 70%) - Repair Costs

If your ARV is $275,000 and repairs cost $40,000:

• Maximum offer = ($275,000 × 0.70) - $40,000
• Maximum offer = $192,500 - $40,000
• Maximum offer = $152,500

This formula builds in profit margin and holding costs. Your comp accuracy directly determines whether this formula protects or destroys your deal.

Using Rental Comps to Estimate Income

Rental property investors need two types of comps: sold comps (for purchase price) and rental comps (for income projections).

Where to Find Rental Comps

• Zillow Rentals: Filter by beds/baths and check current listings
• Rentometer: Free tool providing rental estimates by address
• Apartments.com: Good for multi-family comps
• Craigslist and Facebook Marketplace: Check active listings
• Property management companies: Call and ask about typical rents
• MLS rental listings: If your agent has access

Analyzing Rental Comps

Pull 5-10 rental listings that match your property:

| Address | Rent | Bed/Bath | Sq Ft | Condition | Days Listed | |---------|------|----------|-------|-----------|-------------| | 123 Oak | $1,650 | 3/2 | 1,800 | Good | 8 | | 456 Elm | $1,575 | 3/2 | 1,850 | Average | 22 | | 789 Maple | $1,700 | 3/2 | 1,900 | Updated | 3 |

Key insights:

• Updated units rent for $1,650-1,700
• Average condition units rent for $1,575-1,600
• Properties sitting 20+ days may be overpriced

Conservative estimate: Use the median rent for properties in similar condition, not the highest. If investing in a $235,000 property in average condition, budget for $1,600/month rent, not $1,700.

Calculating Key Rental Metrics

With sold comps (purchase price) and rental comps (income), you can calculate:

Gross Rent Multiplier (GRM):

• Purchase Price / Annual Rent
• $235,000 / ($1,600 × 12) = $235,000 / $19,200 = 12.2 GRM
• Lower GRM = better value (typically want under 15)

1% Rule:

• Monthly rent should equal 1% of purchase price
• $1,600 / $235,000 = 0.68%
• This property doesn't meet the 1% rule (might still work depending on market)

Tools like Rentzilla can automatically calculate these metrics once you input your comps and purchase details.

Common Mistakes to Avoid With Comps

Even experienced investors make these errors:

1. Using Outdated Comps

Real estate markets move fast. A comp from 9 months ago may reflect a market that's since