What will be your monthly payment on a $500,000 15 and a 30 yr mortgage if the rate is 3.15 % for people with good credit and 9.95% for people with bad credit 4 calculations? (The mortgage is $500,000 (not the price of the house) you will have to adjust bank rate.com default of 20% down to 0% down, 500k mortgage) Also, how much interest will you pay over the life of the 4 loans you just calculated? Why would someone finance a house with a 10 year interest only loan (site 3 reasons)?