We compute a monthly housing allowance from the 28/36 rule: the smaller of front-end (housing ≤ 28% of gross monthly income) and back-end (housing + other debts ≤ 36% of gross monthly income). From the allowance we subtract expected monthly taxes, insurance, HOA, and maintenance — the remainder is available for principal & interest (P&I). We convert that P&I allowance to a loan using mortgage amortization formulas and add the down payment to estimate the max purchase price.