The three numbers that matter
A rental either makes sense on the numbers or it does not, and three figures tell most of the story. Monthly cash flow is what lands in your account after the mortgage and operating costs. Cap rate is net operating income over the purchase price, which lets you compare properties regardless of financing. Cash-on-cash return measures the cash flow against the actual money you put in, which is the return your down payment is earning.
Why financing sits outside the cap rate
Cap rate deliberately ignores the mortgage. Two investors can buy the same building with very different down payments and rates, so financing tells you about the deal structure, not the property. By comparing cap rates you compare the properties themselves. Then cash-on-cash and cash flow bring your specific financing back into the picture.
Run it honestly, then keep the record
The fastest way to talk yourself into a bad deal is to assume full occupancy and no repairs. Build in vacancy and a maintenance reserve, and the cash flow gets more honest. Once you own the property, the same discipline pays off: tracking rent, maintenance, and costs in one place is what turns a guess into a real return you can measure year over year. For the deductible side of those costs, see our guide to rental property tax deductions in Canada.