The Same Building, Two Different Truths: A $500K fourplex with $30K NOI is a 6% cap rate deal to one investor and a 14% cash-on-cash deal to another. Cap rate measures the asset. Cash-on-cash measures what happened to your wallet. Why Cap Rate Doesn't Care About Your Loan: NOI divided by purchase price. Strips out financing noise so you can compare a $300K duplex against a $1.2M apartment on equal footing. The sanity check on whether the underlying real estate is actually a better asset. Cash-on-Cash: Where Leverage Sneaks In: All cash gets you a 6% return that equals the cap rate. 25% down nudges it to 10%. 10% down can push to 22% — or negative, depending on rates. Same building, different financing, completely different returns. The Trap Nobody Warns Beginners About: An 18% cash-on-cash deal at 90% LTV flips to negative the month a HVAC compressor fails or insurance renews 35% higher. Pros stress-test cash-on-cash against vacancy, rate hikes, and surprise repairs before they sign. Calculate Both, Always: A 9% cap rate with a 4% cash-on-cash is a warning — financing is eating your returns. A 5% cap rate with 14% cash-on-cash means you're dependent on cheap debt. The two numbers together tell the deal's full story.