How much would you have to put down on a house costing $100,000 if the house had an appraised value of $91,000?

Also, Using the maximum ratios for a conventional mortgage, how big a monthly payment could the Bacon family afford if their gross (before-tax) monthly income amounted to $4,500? Would it make any difference if they were already making monthly installment loan payments totaling $550 on two car loans?