“It would be cool to have a house downpayment % option (instead of just $ value), and the ability to “lock in” a 30 year pay off period (without it auto-adjusting). That way you can easily experiment with different house prices on a 30 year fixed mortgage without having to change a bunch of fields in the form. Right now if you adjust the price of a house you need to (1) calculate the downpayment and enter it again, (2) reset the years to pay off to 30 again.”