Is cap rate the same as ROI?

No. Cap rate is net operating income divided by price, before any financing, and measures the property's unleveraged yield in one year. ROI on a rental usually means total return on the cash you invested, including the loan, appreciation and principal paydown over the holding period.

Cap rate ignores how you paid, so two buyers at the same cap rate earn very different returns on cash. It also ignores appreciation and paydown, often most of a rental's total return.

Cash on cash return is the leveraged one-year version: cash flow after the mortgage divided by cash invested. Total ROI adds appreciation and paydown. IRR spreads it across the holding period. A 6% cap rate property might produce a 4% cash on cash return at 25% down and an 18% first-year total ROI once appreciation and paydown are counted. Cap rate is the starting point, not a substitute.