The first lesson is the big one: a pre-approval quote is not a rate lock. A true lock means an issued Loan Estimate showing the lock box checked and the lock duration stated. Without that document in hand, your rate floats with the market. The earlier quote wasn't honored because it was never locked (or no long advance lock was ever offered), and that's the core issue, separate from who the lender is. The builder piece is worth understanding too. A builder's preferred lender is often paying points out of the builder's incentive budget to buy the quoted rate down. An outside broker can't match that number without charging you comparable points, because the broker never receives the builder's incentive money to subsidize the buydown. That doesn't automatically make the preferred lender the better deal. To check it: - Have an outside lender price the exact same scenario. - Compare rate plus total closing costs side by side, including the value of any builder incentive you'd give up by going elsewhere. - Get it in writing on a Loan Estimate. And don't consider yourself protected until the lock is documented.