Take-home, not the 28/36 gross rule
Classic affordability rules use gross income. This page uses take-home because that is the money that actually pays the mortgage, tax, insurance, and remaining debts. A household with a large 401(k) deferral has less take-home than the salary implies.
Comfortable, stretch, and aggressive bands are CostAnswer thresholds on net pay. A lender may approve a loan that this page labels aggressive, or deny one this page labels comfortable. Credit, reserves, and property type are not in the model.