The spreadsheet is where emotions go to die — and where good deals get separated from expensive mistakes. Here is how to analyze a rental property with precision.
Experienced investors use several metrics to evaluate deals, each measuring something slightly different. Understanding what each one tells you — and when to use it — is fundamental to making confident purchase decisions.
Cash flow is the simplest and most important metric: how much money is left each month after all expenses are paid. It is not gross rent. It is not rent minus mortgage. It is rent minus every single expense including vacancy, repairs, and management.
Gross Rent
− Vacancy (typically 5–8% of gross rent)
− Property Management (8–10% if using a PM)
− Property Taxes
− Insurance
− Maintenance Reserve (typically 10% of gross rent)
− CapEx Reserve (typically 5–10% of gross rent)
− Mortgage (PITI)
= Monthly Cash Flow
Most rookie investors forget vacancy, maintenance reserves, and capital expenditure (CapEx) reserves. This is why deals that looked great on paper bleed cash in practice. Always include them. A good rule of thumb: budget 40–50% of gross rent for all expenses before debt service.
Cap rate (capitalization rate) measures a property's income potential independent of financing. It tells you what the property would return if you paid cash — which makes it useful for comparing properties regardless of how they are financed.
Cap Rate = Net Operating Income ÷ Property Value
NOI is gross rent minus all operating expenses except the mortgage. A $200,000 property generating $14,000 in annual NOI has a 7% cap rate. Cap rates vary significantly by market — 4–5% is normal in expensive coastal cities, 7–9% is common in the Midwest and South. Neither is inherently better; they reflect market-specific appreciation expectations.
Cash-on-cash return measures the annual cash flow as a percentage of the cash you actually invested. This is what most investors care about most — it tells you what your down payment is earning.
Cash-on-Cash = Annual Cash Flow ÷ Total Cash Invested
If you put $40,000 down and your annual cash flow is $4,800, your cash-on-cash return is 12%. Most experienced investors target 6–10% cash-on-cash as a minimum threshold, though in competitive markets 4–6% is sometimes acceptable given strong appreciation potential.
The 1% rule is a quick screening filter: monthly rent should be at least 1% of the purchase price. A $150,000 property should rent for at least $1,500/month. This is not a buying rule — it is a filtering rule to quickly eliminate deals that clearly will not cash flow.
In many markets today, 1% is nearly impossible to achieve. That does not mean every sub-1% deal is bad. It means you need to run the full numbers rather than relying on the shortcut.
GRM is a rough valuation tool: divide the purchase price by annual gross rent. Lower GRM means better value. A property selling for $180,000 with $18,000 in annual gross rent has a GRM of 10. Use this to quickly compare properties in the same area — it does not account for expenses, so do not use it alone.
A solid buy and hold deal in most markets: the 1% rule is close to met, cash-on-cash return is 6%+ after conservative expense assumptions, and the neighborhood supports stable occupancy. You can make money on deals that miss one of these — but missing all three usually means you are overpaying for the asset.