Real estate investing has a seduction problem. Beautiful listing photos, exciting appreciation projections, and the promise of "passive income" make people fall in love with properties before doing the math. The math is what separates investors who build wealth from investors who own expensive headaches.
A proper rental property analysis takes about five minutes and three key metrics: monthly cash flow, cap rate, and cash-on-cash return. If a property doesn't pass all three, it doesn't matter how nice the kitchen looks.
Monthly Cash Flow: The Number That Keeps You Alive
Cash flow is rental income minus all expenses — mortgage payment, property taxes, insurance, maintenance, property management fees, vacancy allowance, and HOA if applicable. Positive cash flow means the property pays for itself and puts money in your pocket. Negative cash flow means you're subsidizing your tenants' housing out of your own income every single month.
The mistake most new investors make is underestimating expenses. They calculate mortgage plus taxes and call it done. But maintenance typically runs 1-2% of property value annually. Vacancy averages 5-10% depending on the market. Property management takes 8-10% of rent. Insurance, HOA, and unexpected repairs add up. A property that "cash flows $500/month" on a napkin calculation often cash flows $50 — or negative — when you account for everything.
Cap Rate: The Quick Comparison Tool
Cap rate (capitalization rate) is your net operating income divided by the purchase price. It strips out financing and gives you an apples-to-apples way to compare properties. A $300,000 property generating $24,000 in annual net operating income has an 8% cap rate. A $500,000 property generating the same $24,000 has a 4.8% cap rate. The first property is working harder for you relative to the capital invested.
In most US markets, cap rates currently range from 4% to 10%. Below 4% is generally a poor investment from a cash flow perspective — you're betting entirely on appreciation. Above 7% is attractive. Above 10% might signal a problem the seller isn't disclosing.
Cash-on-Cash Return: Your Real ROI
Cash-on-cash return measures your annual pre-tax cash flow divided by the total cash you invested (down payment, closing costs, and any renovation). This is the number that tells you what your actual money is earning. If you put $60,000 into a property and it generates $6,000 in annual cash flow, your cash-on-cash return is 10%.
This metric accounts for leverage in a way cap rate doesn't. A property with a modest cap rate can have an excellent cash-on-cash return if you finance it well, because you're controlling a $300,000 asset with $60,000 of your own money. Leverage amplifies returns in both directions — great when prices rise, painful when they fall.
Want to analyze a specific property? Our free Rental Property ROI calculates monthly cash flow, cap rate, cash-on-cash return, and a 5-year projection including appreciation and equity buildup. Plug in the numbers from any listing and see whether it's a deal or a disappointment.