How much interest will I really pay over the life of my mortgage?

Far more than most people expect. On a $400,000 30-year loan at 7%, the total interest can exceed $550,000 – meaning you repay well over double what you borrowed. The total depends heavily on your rate and term: the same loan at a lower rate or on a 15-year schedule cuts interest dramatically. This is why extra principal payments, even modest ones early on, save so much: every dollar of principal you knock out removes years of compounding interest on it. Ask your lender for a full amortization schedule so you can see the lifetime interest in black and white, then test how one extra payment a year changes the total. The number is often the motivation people need to pay down faster.