Do you know what your payment will be after the reset?
Assuming that interest rates will remain the same as they are today
(too simplistic), the following calculator computes mortgage payments
before and after reset.
http://csharpcomputing.com/webapps/arm.jsp
For example, if today loan amount 450000, interest rate 4.125%, loan
is 5/1 ARM, and it is due to reset next year, then monthly payment
before reset is $2354 and after reset is $3247
Hope it is useful,
Martin