USDA loans are grouped into Ginnie Mae bond pools, along with FHA loans. While the rates are not identical, typically they will move in relatively the same degrees. Can certainly appreciate your dilemma, hopefully builder will get going soon (hard to think house will be done 10/1 if not started yet!), and at least rates have stabilized for the moment. I would certainly be in close contact with your builder, if he wants to sell you the house, he has to build it first!