The honest answer: less than you probably think. But rates are tiered — so the higher your score, the better the pricing you'll see.
Program minimums: FHA starts at 580 (with 3.5% down) and can go to 500 with 10% down. VA and USDA have no set minimum, but most lenders overlay 580-620. Conventional generally starts at 620.
Where rates actually change: credit is tiered in 20-point brackets on conventional loans — 620-639, 640-659, 660-679, 680-699, 700-719, 720-739, 740+. Each bracket up can move your rate by 0.125% to 0.5%.
The tier that matters most: 740+. That's the top pricing bucket for most conventional programs. If you're at 720, spending 60 days to reach 740 can pay for itself many times over.
For FHA, the big brackets are 580, 640, and 680. Below 640, some lenders won't offer their full menu of programs.
The takeaway: don't wait for a 'perfect' score before starting the conversation — but do know that 60 days of focused work on your credit before applying can meaningfully change your monthly payment.