Your protection is the Loan Estimate plus a backup lender kept warm in parallel. The Loan Estimate sets legal tolerances on how much various fees are allowed to change between disclosure and closing, so it's your paper trail if the builder's lender starts moving numbers. The new-construction complication: the loan usually can't be locked until you're close to completion, and homes can take months to finish. The rate and some costs legitimately float during that stretch and can shift with the market. Because capturing the builder incentive (say a credit toward closing costs) often requires using their preferred lender, don't take that lender's word that their deal is best. Keep your trusted lender's file open at the same time, and have them review the builder lender's final Loan Estimate at lock, so you can compare the two like for like on the same day. Incentives are frequently worth less than advertised once you net them out. We've seen a headline builder credit around $30,000 come out closer to $18,000 in real value once the rate and fees were compared apples to apples. Get the final numbers in writing, compare them side by side at lock, and let the better real deal win.