no one is going to do that for 4% They will if you pay them to do it upfront. In other words; for a $400k home, the difference in interest between a 4% loan a

no one is going to do that for 4% They will if you pay them to do it upfront. In other words; for a $400k home, the difference in interest between a 4% loan and a 5% loan over 30 years is worth maybe $20k in today's dollars (just a guesstimate, I haven't done the actual math). So all the builder needs to do to make this magic happen is markup the sales price of his $400k home by 5% and use the additional cash to buy the rate down. Basically, it's just marketing BS made possible by the time value of money.