There are thousands of potential short-term rental markets in the U.S. Deep-diving each one takes hours. If you don't have a fast way to separate the contenders from the time-wasters, you'll burn weeks on markets that were never going to work.

You need a filter. One number that tells you, in minutes not days, whether a market deserves your attention.

That number is 20%.

What the 20% Price-to-Rent Ratio Means

The math is simple: divide a property's estimated annual short-term rental revenue by its purchase price. If the result is 20% or higher, the property will likely cash flow.

A $500,000 home generating $100,000 per year? That's a 20% ratio. At an 8% interest rate with typical expenses, that property produces roughly 10% cash-on-cash return.

Not glamorous. But consistent, real, and bankable.

What Happens Above and Below 20%

The 20% mark isn't arbitrary. It's the line where the math either works or collapses.

At 24% (the upside): A $500,000 property earning $120,000 per year pushes cash-on-cash returns into the 20-30% range. This is where experienced investors get excited. These deals exist, but your baseline should hit 20% before you start hoping for 24%.

At 16% (the downside): That same $500,000 property earning only $80,000 per year? You're losing money. Not breaking even. Losing money. The gap between 20% and 16% doesn't feel large, but it's the difference between a profitable asset and a financial drain.

This is why "close enough" is dangerous. An 18% ratio feels almost there. But run the numbers through a full underwriting model, mortgage, insurance, property management, maintenance, utilities, supplies, and "almost there" means negative cash flow in a below-average month.

STRProfitMap's Property Analyzer calculates NOI, Cap Rate, Cash-on-Cash Return, and DSCR automatically, so you can verify whether a property clears the 20% threshold with real expense modeling.

Use Your Worst Case, Not Your Best Case

Here's where most investors fool themselves: they use their optimistic revenue estimate as the baseline.

Don't. Your 20% number should be the revenue figure you're 100% confident the property will hit. Not your best-case projection. Not what the top-performing listing in the market earns. The number you'd bet your mortgage payment on.

If your confident estimate hits 20%, your best case will be higher and your worst case will still be survivable. If you need your best case to hit 20%, you're one slow season away from writing checks instead of cashing them.

The Two-Step Market Screening Process

Once you understand the 20% rule, you can screen any market in two steps.

Step 1: Find an Average Property With Reliable Data

Search your target market and filter by property type (entire home) and one bedroom count at a time. Mixing bedroom counts creates noise.

Sort by revenue and scroll until you find a property that is:

Average in quality. Not a luxury estate. Not a converted barn with a treehouse. A normal, replicable home that any investor could buy and furnish.

Backed by solid data. Look for properties with 100+ reviews and high availability (300+ days). Newer listings with limited history give you unreliable numbers.

Note the annual revenue and study the listing photos. Understand the property's size, finishes, and location. You'll need this context for Step 2.

STRProfitMap's Market Saturation Score tells you whether supply is outpacing demand, an important context when evaluating if historical revenue numbers will hold up.

Step 2: Find a Comparable Property at the Right Price

Take that annual revenue number and divide by 0.20 to get your maximum purchase price. If a listing earns $100,000/year, you need a comparable home priced at $500,000 or less.

Go to Zillow. Set your filters: matching bedroom count, property type, and a maximum price based on your 20% calculation. Draw a circle around the same neighborhood.

Now look at what shows up.

If comparable homes appear at or below your target price: The market has cash flow potential. Add it to your short list for a deep dive.

If nothing comparable shows up: The homes available at that price point aren't remotely similar to the one generating revenue. The market likely doesn't work at this bedroom count. Repeat the process with a different bedroom count or neighborhood before ruling it out entirely.

A Real Example: Atlanta vs. Boise

In Atlanta, a four-bedroom earning $97,000/year had comparable homes available on Zillow in the $500,000 range on the west side of downtown. The 20% math worked. Atlanta went on the short list.

In Boise, a similar search fell flat. Properties earning $63,000/year would need to be priced around $315,000 to hit the 20% rule. The homes available at that price in the same area? A trailer and a much smaller house, nothing comparable to the listing generating that revenue. After repeating the process across multiple bedroom counts and neighborhoods, Boise got cut.

No deep dive needed. No weeks of analysis. The two-step screen gave a clear answer in under 30 minutes.

STRProfitMap's market overview gives you the revenue, occupancy, and home value data you need to run the 20% calculation for any of 20,000+ markets, without toggling between multiple tools.

When to Repeat and When to Move On

If your first pass doesn't produce matches, try:

• A different bedroom count (switch from four-bedroom to three-bedroom)
• A different neighborhood within the same market
• A slightly adjusted price range (maybe you can negotiate below list)

If you've run through multiple bedroom counts and neighborhoods with no matches, the market doesn't have the revenue-to-price ratio to support cash flow. Remove it from your list and move to the next candidate.

One confirmed match is enough to justify a deeper analysis. Two or three matches give you high confidence.

The Bottom Line

The 20% price-to-rent ratio is the fastest filter in short-term rental investing. It won't replace full underwriting. You still need to verify regulations, analyze seasonality, and model expenses in detail before buying. But it will keep you from spending 10 hours deep-diving a market that was never going to pencil out.

Annual revenue divided by purchase price, 20% or higher. That's the threshold. Everything below it is a warning sign.

Want to find markets that pass the 20% test, with detailed revenue data and property-level analysis? Get your custom profit map at STRProfitMap.com and start screening smarter.