If you can make payments of 589.33 per month and your interest rate 4% and you want to buy a car for 32,000.00 how long will it take to pay it off? 12 If buy a house for 150,000.00 with a down payment of 25,000.00 and payments of 700.00 per month for thirty years. What is your annual interest rate? If you want to have two million dollars saved forty years from now and you can save five hundred dollars a month what interest rate do you need to have to reach your goal