The Real Numbers Behind a Rental Property: Cap Rate, Cash Flow and ROI

Cap rate (Net Operating Income ÷ purchase price) measures a property's return independent of how it's financed — it's meant to let you compare properties on equal footing regardless of down payment size or mortgage rate. NOI itself deliberately excludes the mortgage payment, since that's a financing decision, not a property-level metric.

Cash flow is what's actually left in your pocket each month after every expense, including the mortgage payment. Two properties with identical cap rates can have very different cash flow depending on how they're financed — a larger down payment means a smaller mortgage payment and higher cash flow, even though the property's own performance (cap rate) hasn't changed.

Cash-on-cash return (annual cash flow ÷ total cash invested) measures the return on the actual dollars you put in — down payment plus closing costs — rather than the full purchase price. This is often the most personally relevant number, since it reflects your specific financing structure.

It's common, especially in expensive Canadian markets, for a property to have a perfectly reasonable cap rate while still producing negative monthly cash flow once financing is factored in. That's not automatically a bad investment — some investors accept it in exchange for expected appreciation and principal paydown — but it does mean budgeting for a real, ongoing monthly shortfall, not a surprise one.