A lender counts your actual student loan payment, or in some cases a minimum percentage of the outstanding balance if you are on an income-based repayment plan, against that 44 percent total debt service limit, so a large student loan balance can reduce how much mortgage you qualify for even with a strong income.
A minimum credit score of 600 is required for an insured mortgage regardless of how the ratios work out, and an individual lender can apply a stricter internal limit than the CMHC guideline minimum depending on the rest of the file, so two buyers with identical student loan balances can still qualify for different mortgage amounts.
Joel Dyck connects buyers with a mortgage broker who can run their exact student loan numbers against both ratios before they start looking at homes. Get your hand-reviewed valuation from Joel Dyck.