CMHC looks for a gross debt service ratio around 39 percent of income and a total debt service ratio around 44 percent, so a 600 score paired with heavy car or credit card payments can still produce a smaller approved amount than the score alone would suggest.
Down payment source matters too. Savings, a gift or a Home Buyers' Plan withdrawal of up to $60,000 are all treated differently by a lender, and a newer FHSA, which allows up to $8,000 a year to a $40,000 lifetime limit, is now part of that mix for many first-time buyers.
A 600 score gets you in the door; the file around it decides what you actually qualify for. Get your hand-reviewed valuation from Joel Dyck.