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Summary: A basement apartment can help cover your mortgage, but only if it is a legal second unit. Ontario now allows up to three residential units on most serviced lots, yet many existing basement apartments were never permitted — and that becomes the buyer's problem.
The rental income is the draw, and it is real. The risk is that legality is invisible at a showing: a finished, tenanted basement can still be an unpermitted unit the municipality could order closed. Knowing what to check before you waive your conditions is what protects you.
What is a legal second unit in Ontario?
A second unit, or additional residential unit, is a self-contained dwelling with its own kitchen, bathroom, and entrance inside or alongside a house. Since Ontario Regulation 462/24 took effect in late 2024, most residential lots on full municipal servicing can have up to three units as of right.
"As of right" means the units are permitted without a rezoning, though you still need building permits and the units still have to meet the building and fire codes. A unit that exists on paper and in the zoning by-law is very different from a finished basement someone rented out without ever pulling a permit.
What makes a basement apartment legal, or not?
A separate entrance and a tenant do not make a unit legal. Legality comes from meeting several standards at once, and a gap in any of them can make the unit unpermitted.
Zoning. The lot must allow a second unit, which most Ontario residential lots now do as of right.
Building permit. The unit must have been built or converted under a permit and passed inspection.
Fire Code retrofit. Two-unit houses must meet the Ontario Fire Code retrofit rules for two-unit residential occupancies: fire separations, two means of escape, and interconnected smoke and carbon monoxide alarms.
Electrical safety. The wiring should have an Electrical Safety Authority (ESA) inspection and certificate.
Physical standards. Minimum ceiling height, window size for egress, and separate suite requirements all apply.
Legal vs unpermitted second unit: why it matters for a buyer
The difference decides whether the apartment is an asset or a liability. A legal unit supports your financing and your insurance; an unpermitted one can be ordered closed and can complicate both.
Legal second unit | Unpermitted unit | |
Rental income toward your mortgage | Lenders may count a portion | Usually not counted |
Home insurance | Covered when disclosed | Coverage can be denied or voided |
Municipal risk | Compliant | Can be ordered closed or brought up to code |
Resale | A selling feature | A problem you pass to the next buyer |
How do you check a basement apartment before you buy?
Because none of this shows at a viewing, build the checking into your offer. Treat the conditional period as the window to confirm the unit is what the listing implies.
Ask for the paperwork. Request the building permit, final inspection, Fire Code retrofit confirmation, and ESA certificate for the unit.
Confirm zoning with the municipality. Verify the lot allows a second unit and that the existing one is recognized.
Add a condition. Make the offer conditional on verifying the unit's legal status, and have your lawyer review the agreement of purchase and sale so the wording protects you.
Get an inspection that covers the unit. A home inspector can flag missing egress, fire separation, and electrical issues.
Review any existing lease. If the basement is already rented, get the lease and the tenant's details before you commit.
For the wider process, our guide for first-time home buyers in Ontario walks through conditions, financing, and closing.
What happens to the tenant if the home is already rented?
If the basement apartment comes with a tenant, the tenancy transfers to you at closing under the Residential Tenancies Act, 2006. You become the landlord on the existing terms, and you cannot simply end the tenancy because ownership changed.
You can ask the seller to deliver the unit vacant, or you can keep the tenant. If you want the unit for your own or a family member's use, the Act sets out a specific notice (Form N12), a notice period, and one month of compensation. Plan this before you sign, not after.
Frequently asked questions
Can I count the basement rental income toward my mortgage?
Sometimes. Lenders may count a portion of documented rental income from a legal unit toward your qualifying income. Income from an unpermitted unit usually will not count and can make approval harder, so confirm the unit's status early with your mortgage advisor.
Is a basement apartment legal just because it has a separate entrance?
No. A separate entrance is only one piece. A legal unit also needs zoning permission, a building permit, Fire Code retrofit compliance, and electrical safety approval. Many rented basements have the entrance but not the paperwork.
What happens if I buy a house with an illegal basement apartment?
You inherit the compliance risk. The municipality can require the unit to be brought up to code or closed, and the cost and disruption fall on you as the new owner. That is why verifying legality before closing matters.
Does the tenant have to move out when I buy?
Not automatically. The tenancy transfers with the property, and you take over as landlord. You can only end it in limited situations, such as needing the unit for your own use, which requires proper notice and compensation under the Residential Tenancies Act, 2006.
How many units can I have on my lot in Ontario?
On most residential lots with full municipal servicing, up to three residential units as of right since Ontario Regulation 462/24 took effect in late 2024, for example a main unit, a basement apartment, and a garden suite, subject to local rules.
About the author
Joel Fox is a co-founder and COO at Ownright. He helps run the firm's day-to-day work on Ontario residential closings, refinances, and sales, and writes regularly to demystify the parts of a transaction that most homeowners only encounter once or twice in their lives.
At Ownright, we focus entirely on Ontario residential real estate law, helping buyers and sellers with purchase closings, sales, refinances, and status certificate reviews. Our licensed Ontario lawyers work alongside a digital platform that lets you track your file, sign documents remotely, and reach us by chat, email, or video call. You can start your closing online or get in touch with any questions.
Legal references: Planning Act, R.S.O. 1990, c. P.13 and O. Reg. 462/24 (additional residential units); Fire Code, O. Reg. 213/07 (two-unit residential occupancies); Residential Tenancies Act, 2006, S.O. 2006, c. 17.
Important note: This article is not legal advice. No one should act, or refrain from acting, based solely on the information in this post or any linked materials without first seeking appropriate legal or professional advice.
