Yes, you can co-sign your adult child’s mortgage, which can help them get approved for a loan if their income or credit score is insufficient or if they have too much debt. Keep in mind that you’re fully on the hook for the mortgage if something happens and your child becomes unable to pay it back. Co-signing will also affect your own debt-to-income (DTI) ratio, which can affect your future ability to be approved for things like a mortgage or an auto loan.