A few things you need to concern: 1. If the builder's lender has any "jail" time for you. Usually it is 4-6 months that you have to stay with current lender. 2. Even the current lender is OK for you to refinance at any time right after the closing, but the new lender might have some restriction for you such as: You have to be on title for certain of the month, OR you have to pay the cerntain months mortgage payments... So it is really depend on current lender and feature's new lenders you choose. Since the rate is low and stable lately, there do have many customers requst to get as much as rebate they could to cover the closing cost and then refinance in 4-6 months period to get lower rate. Just provid those information as your reference. Good luck!