<prompt> Human: We are purchasing home in HCOL with 1.17 M mortgage. We are getting 3.625 for 7 ARM vs 4.25 for 30 year fix for the amount we are borrowing. Payment difference between 30 year and 7 ARM is about 400 5,301 for 7 ARM vs 5,718 for 30 year. We would like to pay off this home in less than 30 years if possible. Most likely 15-20 years . One Idea we had was to go with 7 year arm and keep pumping additional payments till next 7 year and reduce our loan balance. We refinance between year 5 - 7 depends on where interest rates are. This strategy assumes we will be able to lock lower interest rate within next 6 years. We do not want to wait till last year until it is definitive that rates will be lower before our reset hit. Other things to consideration is that if we refinance in next 5-6 years, we will be resetting our amortization and paying more interest in beginning. Given that interest rates are going up, should we lock in lower 30 year fix or try to bet on future lower rates while we pay additional principle. ?x200B;  <response>: I highly doubt you will see lower interest rates over the next several years. I think youd be better off locking in the 30. You should be able to swing an extra 400 a month if not, youre already purchasing too much house even in a high COL area, and then you wont have to worry about getting clobbered once the ARM starts floating. 