Can’t you get a 10 year I/O that has a fixed rate and at year 11, your loan is then amoratized for 20 years at the same rate? You pretty much turn it into a 20 eyar fixed rate loan. With my calculations your per month price would go up %30. If you can plan and save , then when the 10 years is up you should be able to make up the %30 increase per month.