Mortgage Approval 101: GDS & TDS Explained

Darrell McCollom • October 15, 2025

Can You Afford That Mortgage? Let’s Talk About Debt Service Ratios

One of the biggest factors lenders look at when deciding whether you qualify for a mortgage is something called your debt service ratios. It’s a financial check-up to make sure you can handle the payments—not just for your new home, but for everything else you owe as well.


If you’d rather skip the math and have someone walk through this with you, that’s what I’m here for. But if you like to understand how things work behind the scenes, keep reading. We’re going to break down what these ratios are, how to calculate them, and why they matter when it comes to getting approved.


What Are Debt Service Ratios?

Debt service ratios measure your ability to manage your financial obligations based on your income. There are two key ratios lenders care about:

  1. Gross Debt Service (GDS)
    This looks at the percentage of your income that would go toward housing expenses only.

   2. Total Debt Service (TDS)
       This includes your housing costs plus all other debt payments—car loans, credit cards, student loans, support payments, etc.


How to Calculate GDS and TDS

Let’s break down the formulas.


GDS Formula:

(P + I + T + H + Condo Fees*) ÷ Gross Monthly Income


Where:

P = Principal

I = Interest

T = Property Taxes

H = Heat


Condo fees are usually calculated at 50% of the total amount


TDS Formula:

(GDS + Monthly Debt Payments) ÷ Gross Monthly Income


These ratios tell lenders if your budget is already stretched too thin—or if you’ve got room to safely take on a mortgage.


How High Is Too High?


Most lenders follow maximum thresholds, especially for insured (high-ratio) mortgages.

As of now, those limits are typically:

GDS: Max 39%

TDS: Max 44%


Go above those numbers and your application could be declined, regardless of how confident you feel about your ability to manage the payments.


Real-World Example

Let’s say you’re earning $90,000 a year, or $7,500 a month.

You find a home you love, and the monthly housing costs (mortgage payment, property tax, heat) total $1,700/month.


GDS = $1,700 ÷ $7,500 = 22.7%


You’re well under the 39% cap—so far, so good.


Now factor in your other monthly obligations:

  • Car loan: $300
  • Child support: $500
  • Credit card/line of credit payments: $700
    Total other debt = $1,500/month


Now add that to the $1,700 in housing costs:
TDS = $3,200 ÷ $7,500 = 42.7%


Uh oh. Even though your GDS looks great, your TDS is just over the 42% limit. That could put your mortgage approval at risk—even if you’re paying similar or higher rent now.


What Can You Do?

In cases like this, small adjustments can make a big difference:

  • Consolidate or restructure your debts to lower monthly payments
  • Reallocate part of your down payment to reduce high-interest debt
  • Add a co-applicant to increase qualifying income
  • Wait and build savings or credit strength before applying


This is where working with an experienced mortgage professional pays off. We can look at your entire financial picture and help you make strategic moves to qualify confidently.


Don’t Leave It to Chance

Everyone’s situation is different, and debt service ratios aren’t something you want to guess at. The earlier you start the conversation, the more time you’ll have to improve your numbers and boost your chances of approval.


If you're wondering how much home you can afford—or want help analyzing your own GDS and TDS—let’s connect. I’d be happy to walk through your numbers and help you build a solid mortgage strategy.


Darrell McCollum

First-Time Buyer? Here’s How to Tell If You’re Ready

By Darrell McCollom • December 3, 2025
Ready to Buy Your First Home? Here’s How to Know for Sure Buying your first home is exciting—but it’s also a major financial decision. So how can you tell if you’re truly ready to take that leap into homeownership? Whether you’re confident or still unsure, these four signs are solid indicators that you’re on the right path: 1. You’ve Got Your Down Payment and Closing Costs in Place To purchase a home in Canada, you’ll need at least 5% of the purchase price as a down payment. In addition, plan for around 1.5% to 2% of the home’s value to cover closing costs like legal fees, insurance, and adjustments. If you’ve managed to save this on your own, that’s a great sign of financial discipline. If you're receiving help from a family member through a gifted down payment , that works too—as long as the paperwork is in order. Either way, having these funds ready shows you’re prepared for the upfront costs of homeownership. 2. Your Credit Profile Tells a Good Story Lenders want to know how you manage debt. Before they approve you for a mortgage, they’ll review your credit history. What they typically like to see: At least two active credit accounts (trade lines) , like a credit card or loan Each with a minimum limit of $2,000 Open and active for at least 2 years Even if your credit isn’t perfect, don’t panic. There may still be options, such as using a co-signer or working on a credit improvement plan with a mortgage expert. 3. Your Income Can Support Homeownership—Comfortably A steady income is essential, but not all income is treated equally. If you’re full-time and past probation , you’re in a strong position. If you’re self-employed, on contract, or rely on variable income like tips or commissions, you’ll generally need a two-year history to qualify. A general rule: housing costs (mortgage, taxes, utilities) should stay under 35% of your gross monthly income . That leaves plenty of room for other living expenses, savings, and—yes—some fun too. 4. You’ve Talked to a Mortgage Professional Let’s be real—there’s a lot of info out there about buying a home. Google searches and TikToks can only take you so far. If you're serious about buying, speaking with a mortgage professional is the most effective next step. Why? Because you'll: Get pre-approved (and know what price range you're working with) Understand your loan options and the qualification process Build a game plan that suits your timeline and financial goals The Bottom Line: Being “ready” to buy a home isn’t just about how much you want it—it’s about being financially prepared, credit-ready, and backed by expert advice. If you’re thinking about homeownership, let’s chat. I’d love to help you understand your options, crunch the numbers, and build a plan that gets you confidently across the finish line—keys in hand.

Home Reno Dreams? Let’s Talk Mortgage Financing

By Darrell McCollom • November 26, 2025
How to Use Your Mortgage to Finance Home Renovations Home renovations can be exciting—but they can also be expensive. Whether you're upgrading your kitchen, finishing the basement, or tackling a much-needed repair, the cost of materials and labour adds up quickly. If you don’t have all the cash on hand, don’t worry. There are smart ways to use mortgage financing to fund your renovation plans without derailing your financial stability. Here are three mortgage-related strategies that can help: 1. Refinancing Your Mortgage If you're already a homeowner, one of the most straightforward ways to access funds for renovations is through a mortgage refinance. This involves breaking your current mortgage and replacing it with a new one that includes the amount you need for your renovations. Key benefits: You can access up to 80% of your home’s appraised value , assuming you qualify. It may be possible to lower your interest rate or reduce your monthly payments. Timing tip: If your mortgage is up for renewal soon, refinancing at that time can help you avoid prepayment penalties. Even mid-term refinancing could make financial sense, depending on your existing rate and your renovation goals. 2. Home Equity Line of Credit (HELOC) If you have significant equity in your home, a Home Equity Line of Credit (HELOC) can offer flexible funding for renovations. A HELOC is a revolving credit line secured against your home, typically at a lower interest rate than unsecured borrowing. Why consider a HELOC? You only pay interest on the amount you use. You can access funds as needed, which is ideal for staged or ongoing renovations. You maintain the terms of your existing mortgage if you don’t want to refinance. Unlike a traditional loan, a HELOC allows you to borrow, repay, and borrow again—similar to how a credit card works, but with much lower rates. 3. Purchase Plus Improvements Mortgage If you're in the market for a new home and find a property that needs some work, a "Purchase Plus Improvements" mortgage could be a great option. This allows you to include renovation costs in your initial mortgage. How it works: The renovation funds are advanced based on a quote and are held in trust until the work is complete. The renovations must add value to the property and meet lender requirements. This type of mortgage lets you start with a home that might be more affordable upfront and customize it to your taste—all while building equity from day one. Final Thoughts Your home is likely your biggest investment, and upgrading it wisely can enhance both your comfort and its value. Mortgage financing can be a powerful tool to fund renovations without tapping into high-interest debt. The right solution depends on your unique financial situation, goals, and timing. Let’s chat about your options, run the numbers, and create a plan that works for you. 📞 Ready to renovate? Connect anytime to get started!