Answer
Use a mortgage calculator to figure your loan out as a fixed rate. get the amoritization table and start making principal payments as figured out by the calculator. when the interest only period ends, as has been stated, you have two choices- the cheaper being to refi in another interest only or begin making much larger payments because your loan has reset to a fully amoritized mortgage and there are fewer years left for repayment. your payment will skyrocket at this point.
start making principal payments and refi into a fixed rate asap!!!
