Yes, the debt still matters. On a 12-unit building the test shifts from your income to the property's. A building that size puts you in commercial lending, where the key metric is the debt service coverage ratio (DSCR) rather than your personal debt-to-income. Instead of asking whether your paycheck covers the payment, the lender asks whether the building covers itself: does the combined rent from all 12 units comfortably exceed the mortgage payment? DSCR is that comparison expressed as a number. A ratio of 1.25 means the property's net income is 1.25 times the debt payment, a real cushion above the mortgage. Tolerances vary by lender: some want around 1.25, some accept 1.1, and some go as low as 0.9, where the building doesn't quite cover its own payment and you'd feed it from other income. The trade-off mirrors personal lending. Thinner coverage reads as more risk, the same way a higher personal DTI does on a primary residence, so it tends to bring a higher rate or tighter conditions. The down payment gets you to the table; the property's income decides your terms.