How existing debt shrinks your buying power
Every dollar of monthly debt payment is a dollar taken out of your Total Debt Service (TDS) ceiling. CMHC caps TDS at 44% for insured mortgages. So a $500/month car payment uses $500 of TDS room directly. On stress-test math, $500/month of TDS translates to roughly $75K-$85K of lost qualifying mortgage. Most first-time buyers underestimate how much existing debt constrains their purchase ceiling.
What counts as debt for qualifying
- Car loans. Monthly payment used at face value. The biggest single debt impact for most first-time buyers.
- Student loans. Monthly payment used at face value. Often skipped by first-time buyers who think government student loans don't count — they do.
- Credit card balances. Lenders use 3% of the balance as the monthly minimum (even if your actual minimum is lower). A $5,000 balance counts as $150/month.
- Personal lines of credit. Monthly minimum used at face value, or 3% of balance if no fixed minimum.
- HELOCs. Treated as fully drawn at the stress-test rate, amortized over 25 years. A $100K HELOC limit you've never used can shrink your qualifying mortgage by $40K-$60K.
- Spousal/child support. Court-ordered payments included in TDS.
The car-loan trap
We see this most weeks. A buyer pre-approves for $750K. They decide to upgrade their car a month before completion, financing a $40K vehicle at $650/month over 7 years. The new debt re-runs their TDS at the lender. The approval drops by $100K. The deal falls through. Do not take on new debt between pre-approval and completion. If you need a new car, wait until after possession.
The undrawn HELOC trap
An undrawn HELOC counts as fully drawn for qualifying. If you have a $100K HELOC limit on your line of credit but have never used it, lenders will still treat the full $100K as outstanding debt at the qualifying rate. Close any unused HELOCs before applying for a mortgage. We've seen this single move add $50K to a buyer's qualifying mortgage.
How to use this calculator
Plug in your household income, target down payment, and each existing monthly debt obligation. The calculator returns your maximum qualifying mortgage with and without each debt line. Use it to see which specific debts are costing you the most buying power. Book a 20-minute chat with the FRIVE team if you want help mapping a debt-paydown strategy to a purchase target.
Frequently asked questions
Should I pay off my car loan before buying a home?
Almost always yes if you can. A $500/month car loan costs you $75K-$85K of qualifying mortgage. Paying it off in full before applying restores that buying power. Talk to a mortgage broker about the math for your specific numbers.
What about my credit card balances?
Pay them down to under 30% of limit before applying. Beyond the TDS impact, high balances hurt your credit score, which affects your rate. The double-impact makes credit cards a priority paydown target.
Do leases count as debt?
Car leases: yes. Equipment leases for business: usually no if the business pays directly. Talk to your mortgage broker about your specific lease situation.
What if my debt is in collections?
Most lenders won't approve a mortgage with active collections. Settle and get the collection removed from your credit report before applying. Some collections can be removed via dispute if they're old or inaccurate.
Does the calculator include credit utilization rate?
Indirectly. Credit utilization affects your credit score, which affects your rate. The calculator uses balances directly in TDS but doesn't model the rate impact of credit score separately.
How does a co-signer's debt affect my qualifying?
It doesn't — directly. Your qualifying uses your debts. But if a co-signer is added to the mortgage, the lender will consider both parties' incomes and both parties' debts.
What if I have a business loan or other debt?
Personal guarantees on business debt count toward your TDS. Business debt without personal guarantee usually doesn't. Lenders ask explicitly during the application.
Should I consolidate debt before buying?
Often yes, if it reduces the monthly payment. Consolidating multiple high-interest debts into a single lower-rate installment loan can reduce TDS even if the total debt is unchanged.
What's a reasonable debt-to-income ratio for a first-time buyer?
Mortgage-related housing carry under 35% of gross income, total debt service under 40% (so a buffer below CMHC's 44% TDS ceiling). Buyers who land at the ceiling often feel squeezed in year 2-3.
Will my debt history come off my credit report?
Closed accounts in good standing stay on your report for 6 years. Late payments and collections stay for 6-7 years from the last activity. Lenders look at the full picture, not just current balances.
Sources
- CMHC — Calculating GDS and TDS ratios. cmhc-schl.gc.ca
- Equifax Canada — Credit utilization and credit score basics. equifax.ca
- FRIVE journal — GDS/TDS ratios BC mortgage qualifying. gds-tds-ratios-bc-mortgage-qualifying
