Rental Deal Screener — 30-Second Pass/Fail (1% Rule, 50% Rule, GRM)

How to Use the Rental Deal Screener

1. Enter the purchase price — the asking or contract price for the property.
2. Enter the monthly rent — use current rent if tenant-occupied, or market rent from comparable listings if vacant.
3. Optionally enter estimated monthly expenses if you already know them. Leave at 0 to use the 50% rule as a fast estimate.
4. Read the hero verdict — green "ANALYZE THIS" means the deal passes enough rules to merit full underwriting. Yellow "MARGINAL" means it might work with favorable financing. Red "LIKELY PASS" means it rarely pencils at these numbers.
5. If the deal passes, click "Run a full cash-flow analysis" to underwrite it properly with NOI, cap rate, DSCR, and cash-on-cash return.

The 3 Quick-Screen Rules Every Investor Uses

Before spending hours building a detailed underwriting model, experienced real estate investors run every prospective deal through a 30-second pass/fail screen. Three rules — the 1% rule, the 50% rule, and GRM — filter out the deals that are unlikely to produce positive cash flow before you invest significant time. Deals that pass even two of these three screens deserve a full analysis. Deals that fail all three rarely pencil at realistic financing costs.

The 1% Rule is the most widely used quick filter in residential rental investing. It states that a property's monthly rent should be at least 1% of its purchase price to generate positive cash flow after typical expenses and financing. Formula: Monthly Rent / Purchase Price × 100. A $250,000 property that rents for $2,500/month hits exactly 1.0% — that is the threshold. At 0.8%, you need exceptionally low expenses or very cheap debt to make it work. At 1.2% or higher, positive cash flow is almost assured regardless of market.

The 1% rule originated in an era of lower property prices and higher rent-to-value ratios. In today's expensive coastal markets (San Francisco, New York, Seattle, Los Angeles), almost nothing hits 1%. In Midwest and Sun Belt secondary cities (Cleveland, Memphis, Indianapolis, Birmingham), the 1% rule is routinely achievable. Understanding your market's typical rent-to-price ratio helps calibrate expectations — use the rule as a filter, not a mandate.

The 50% Rule is a rough but reliable estimator for operating expenses: assume approximately 50% of gross rental income is consumed by operating expenses (property taxes, insurance, vacancy, maintenance, management, and CapEx reserves). The remaining 50% goes toward debt service and cash flow. If 50% of monthly rent exceeds the monthly mortgage payment, the deal has a reasonable chance of positive cash flow. This rule holds up surprisingly well across diverse markets — even when individual expense line items differ — because total expenses tend to converge near 40–55% of gross rent for stabilized residential rentals.

Gross Rent Multiplier (GRM) measures how many years of gross rent it takes to equal the purchase price: GRM = Price / (Monthly Rent × 12). A GRM of 10 means the property costs exactly 10 years of gross rent. Lower is better. GRM under 10 is excellent; 10–14 is good; 14–18 is marginal; above 18 is generally too expensive relative to income. GRM is the inverse of an approximate gross yield: GRM 10 equals 10% gross yield, GRM 12.5 equals 8%. Unlike cap rate, GRM does not account for expenses or vacancy — but it is fast to compute from any listing that shows both price and rent.

When to stop at a screen and when to go deeper: The deal screener answers one question — "is this worth 2 hours of underwriting?" If the deal fails all three metrics, the answer is almost always no (unless you have off-market renovation upside or know something the seller does not). If it passes two or more, open the full cash-flow calculator and run a complete analysis with your actual financing terms, expense estimates, and vacancy assumption. The screen is the front door — the full underwrite is the house tour.

How the Verdict Is Determined

This screener scores three sub-signals and combines them into a single verdict:

1% rule check: passes if monthly rent ÷ price ≥ 0.9% (near-pass is counted; strict 1.0% is the ideal). GRM check: passes if GRM ≤ 11. 50% rule check: passes if 50% of monthly rent is greater than $0 (it always is if rent > 0 — what matters is whether that estimated NOI can cover realistic debt service at current rates). The verdict logic: if 2 or more of these pass, the deal is flagged ANALYZE THIS (green). If exactly 1 passes, it is MARGINAL (yellow). If 0 pass, it is LIKELY PASS (red).

Frequently Asked Questions

• What does it mean if my deal fails the 1% rule but the GRM is low?
  GRM and the 1% rule measure the same thing from different angles — a low GRM (say, 8–9) almost always corresponds to a 1% rule pass. If the GRM is low but the 1% rule still fails, double-check your numbers. If both are in conflict, use the more conservative reading for your initial screen, then run a full model to see if the math works with your actual financing terms.
• Does a deal that passes all three rules guarantee positive cash flow?
  No — the screening rules are heuristics, not guarantees. A deal can pass all three and still produce negative cash flow if financing is expensive (high interest rate, small down payment), expenses are unusually high (deferred maintenance, high property taxes), or vacancy is above average. Always run a full underwrite before making an offer. The screener eliminates the obvious losers; the full model confirms the potential winners.
• What if the 1% rule is impossible in my market?
  In high-price markets (NYC, LA, SF, Seattle), the 1% rule routinely yields 0.4–0.6%. Investors in these markets often rely on appreciation, tax benefits, or forced equity rather than cash flow. If you are investing in a 0.5% market, adjust your benchmark — look for deals at the higher end of the local range, run a full model, and make sure your appreciation assumptions are realistic. The screen can still identify relative value within a market even if the absolute 1% threshold is unachievable.
• How accurate is the 50% rule as an expense estimate?
  Reasonably accurate as a starting point, but it varies. A well-maintained newer property in a low-tax state with self-management might run 35–40% of gross rent. An older property in a high-tax state with professional management and deferred CapEx can easily hit 55–60%. The 50% rule works best as a conservative first screen; always replace it with actual expense estimates when you move to full underwriting. Use this calculator's optional "Est. Monthly Expenses" field when you have real numbers.
• When should I stop at the screen and not do a full analysis?
  If a deal fails all three rules by a meaningful margin (1% ratio below 0.7%, GRM above 16, 50% rule NOI far below realistic debt service), move on — the numbers would require significant rent growth or below-market financing to work, and those are speculative assumptions. Time is your most valuable underwriting resource. The deal screener's job is to protect your time by eliminating deals that are almost certainly not worth a full analysis.
• How do I find the right rent estimate for a property that is vacant?
  Check Zillow Rent Zestimate, Rentometer, or Apartments.com for comparable rentals in the same zip code with similar bedrooms, bathrooms, and square footage. Pull 3–5 comparable active listings and use the median, not the high. If the property needs work before renting, estimate rent at the renovated condition — but account for renovation costs in your price analysis. Accurate rent is the most important input to any rental property model; overstating rent makes every metric look better than it is.