The interest rate for the loan and the length of time it lasts will be 2 more determining factors in your monthly payment. By law the owner can ask up to 11%. To figure an approximate monthly payment of principle and interest on a $112,000 loan in a 30 year mortgage at 11% with $5,000 down -- multiply 107 x $9.52. There are lots of variables to consider. I would suggest contacting a REALTOR (r) for help.