It might seem strange that lenders use gross income instead of net income when determining whether borrowers can afford a mortgage loan. After all, net income is the actual amount of money you bring home each month. But lenders use gross income when qualifying individuals because this is a figure that most consumers readily know. If you make a salary of $72,000 a year, you quickly know that your gross monthly income is $6,000. You might not be able to quickly figure your net income, unless you have your paycheck stub in front of you. Your gross income is also stable, while your net income could change from month to month.