The builder usually has a "preferred lender". Having worked for builders for many years, I can say you will always get the best deal using the builder's lender if the builder is paying the closing costs. A builder's rate may be 1/4 point higher than a bank's rate, but probably the same as a broker's rate. Shopping for rates is very tricky since rates change daily, but if the builder is paying closing costs, it's going to be the best deal. Many people don't realize that there are different rates for different credit scores or different loan programs, but they are all very similar no matter which lender is used.