Secondary suites are becoming a much bigger part of Calgary’s housing market. The City of Calgary says there are now roughly 26,000 registered secondary suites, double the approximately 13,000 on the registry in 2024. The growth has been helped by streamlined approvals and a City incentive program that offered qualifying homeowners up to $10,000 toward creating or legalizing a suite.
As of August 5, Calgary has also made secondary suites a permitted use in low-density residential districts. In practical terms, that removes one potential planning hurdle for homeowners whose projects meet the applicable rules. For homebuyers, however, there is another question worth asking: can the income from that basement suite actually help you qualify for the mortgage? The answer is yes — sometimes quite significantly — but it isn’t quite as simple as adding the expected rent to your salary.
Buyers are actively looking for homes with suites
Secondary suites aren’t just something homeowners think about adding later. CMHC’s 2026 Mortgage Consumer Survey found that 21% of mortgage consumers had a secondary suite. Among homebuyers who had one, 65% said the suite was an important factor when choosing their home.
That doesn’t surprise me. For a first-time buyer trying to make the numbers work in Calgary, a home with a basement suite may offer something a similar home without one doesn’t: another source of income to help offset the mortgage. But there is an important distinction between rent helping you make your monthly payment and rent helping you qualify for the mortgage in the first place.
A lender may be able to use the rental income
Mortgage insurers have specific methods for including rental income when qualifying borrowers. For example, CMHC allows up to 100% of gross rental income to be considered on an owner-occupied two-unit property when the property being purchased is the subject of the mortgage application. Other situations can be treated differently, including properties with three or four units and non-owner-occupied properties.
Sagen similarly allows 100% of rental income for qualifying owner-occupied two-unit properties, subject to its requirements. That can make a meaningful difference. If a basement suite could reasonably rent for $1,500 per month, that’s $18,000 per year in potential rental income. Depending on the lender, insurer, property and mortgage structure, some or all of that income may help with qualification.
But please don’t take that example and immediately add $18,000 to your salary in an online mortgage calculator. Mortgage underwriting enjoys making simple arithmetic more interesting than it needs to be.
The lender still needs to prove the rent
A lender won’t normally accept a number simply because the listing says, “Basement could rent for $1,800!” The rental income may need to be supported by documentation such as an existing lease or market rent determined through an appraisal. Sagen, for example, permits income to be validated using signed leases or fair-market rent from an appraisal for qualifying owner-occupied two-unit properties.
The lender and insurer also have to be satisfied with the property itself. A beautifully finished basement with a fridge and a separate entrance isn’t necessarily a suite that a lender will treat the way you expect.
Registered and compliant suites can make the conversation easier
Calgary’s changes are particularly relevant here. Secondary suites are now permitted uses in low-density residential districts, but they still have to comply with the applicable land-use, building and safety requirements.
That is one reason I would investigate the suite before writing an offer around the assumption that its rental income will make the mortgage work. I want to know whether the suite is registered, what rent the lender is likely to accept, how that income will be calculated and whether the particular lender or insurer we’re using has additional requirements.
Sagen’s current underwriting guidance, for example, says properties should comply with zoning and applicable bylaws, while rental income from an unauthorized suite may be considered on a case-by-case basis. “There’s a tenant downstairs paying $1,600” and “the lender will use $1,600 for qualification” are not necessarily the same statement.
What if you want to build the suite after buying?
That’s another possibility. Mortgage financing can sometimes be structured around improvements to a property, and there are now insured refinancing options specifically designed for homeowners adding secondary suites.
CMHC’s refinance program for building secondary suites allows qualifying homeowners to finance eligible improvements and sets out requirements including plans, cost estimates and permits. Sagen also permits projected rental income from newly built units to be used for qualification under its secondary-suite refinance program when the rent is supported by an appraiser’s fair-market-rent assessment.
That’s potentially useful, but again, it needs to be structured properly. You generally don’t want to buy the house first and figure out whether the financing works later.
A suite can change how much home you can afford
Calgary’s secondary-suite boom isn’t only a story about adding more rental housing. For some buyers, it could change the economics of homeownership.
A house with a suitable basement suite may allow rental income to offset part of the cost of owning the property and, depending on the mortgage program, may also help the buyer qualify for the mortgage. But I wouldn’t shop based on the rent alone.
If you’re considering a Calgary home with a secondary suite, I can run the mortgage numbers using the actual property, expected rental income and the lenders available to you. That tells us whether the suite genuinely increases your purchasing power before you remove financing conditions — which is a considerably better time to find out than the week before possession.
