Are you talking about an existing loan, or taking out a new student loan? If you take out a new loan, before you apply for a mortgage, the lender will see that your credit was run, and ask if you have had any additional credit extended to you. This is where things really get sticky. You would have to show either what your monthly payment will be, or they will take 5% of the balance, and add that to your debt ratio. The same thing applies to things like car loans or leases as well. Even though you were pre-qualified or received a bank pre-approval, all information would be run again and you would have to qualify.