Method 3 Determine Your Maximum Mortgage Level Using the "80% of the Appraised Value of the House" Rule. j. Funds available for the down payment and closing costs $45,000 K Less: Closing costs $10,000 I. Equals: Funds available for the down payment (the 209%) $35,000 m. Times 4: Maximum mortgage level using the "80% of the appraised value of the house" rule (the 20% down, line I, times 4 equals the 80% you can borrow) X4 = $140,000