When you’re applying for a mortgage, your monthly debt obligations play a critical role in determining how much you can borrow. One key factor that lenders evaluate is your debt-to-income (DTI) ratio—the percentage of your gross monthly income that goes toward paying debts. Student loans, even if payments are deferred or set to $0, are always factored into this calculation. Different loan types use varying formulas to estimate your monthly student loan payment, which can significantly affect your borrowing power.