- Properties with one to four residential units are generally treated as residential real estate for financing purposes, including insured mortgage programs designed for owner-occupied and…
- Buying at this scale means your lawyer's due diligence expands well beyond title and survey review: 1.
If you've bought or researched a duplex, triplex, or fourplex in Ontario, buying a 5-plus unit apartment building might look like a bigger version of the same deal. It isn't. The line between four units and five is one of the more consequential thresholds in Ontario real estate investing, because it moves the property out of residential financing and into commercial territory. Buying an apartment building in Ontario at this scale changes how lenders assess the deal, how due diligence works, and how the closing is structured.
This article explains why that threshold matters and what changes once you cross it.
Why 5 Units Is the Legal and Financial Dividing Line
Properties with one to four residential units are generally treated as residential real estate for financing purposes, including insured mortgage programs designed for owner-occupied and small residential properties. Once a building has five or more self-contained units, it's typically classified as a commercial or multi-residential property. That reclassification affects almost every part of the transaction.
How the Rules Change at 5+ Units
| Consideration | 1–4 unit property | 5+ unit apartment building |
|---|---|---|
| Financing type | Residential mortgage, potentially insured | Commercial or multi-residential financing |
| Underwriting basis | Largely the borrower's personal income and credit | Largely the building's income, expenses, and net operating performance |
| Down payment expectations | Can be lower, especially for insured residential mortgages | Typically higher, and lender-specific |
| Appraisal approach | Comparable sales of similar homes | Income-based valuation tied to rents and expenses |
| Legal due diligence | Standard title, survey, and status review | Adds lease review, financial statement review, and often environmental and building condition reports |
| Property management | Often self-managed | Frequently requires a professional management structure |
Due Diligence That Goes Beyond a Standard Purchase
Buying at this scale means your lawyer's due diligence expands well beyond title and survey review:
- Financial due diligence — reviewing rent rolls, operating statements, and expense history to confirm the numbers the seller is presenting.
- Lease review — confirming which tenancies exist, on what terms, and what rights and obligations transfer with the building.
- Building condition and capital planning — understanding the age and condition of major systems (roof, mechanical, electrical), since repairs at this scale are significant capital events, not minor maintenance.
- Compliance review — confirming the building's actual unit count and use match its legal and zoning status, and that fire and building code compliance is in order.
- Environmental review — for older buildings, a professional environmental assessment is common practice before closing on a commercial-scale purchase.
Common Financing Paths for Larger Buildings
Buyers at this scale typically arrange financing through one of a few routes: a conventional commercial mortgage from a bank or credit union, a specialized multi-residential lending program, or private or institutional financing for larger portfolios. Some of these programs are insured, similar in concept to residential mortgage insurance but structured around the building's income rather than an individual borrower's. Because terms, rates, and qualifying criteria vary by lender and change over time, work with a mortgage professional experienced in multi-residential financing rather than assuming your home-purchase experience will transfer directly.
Structuring the Purchase and Closing
Commercial and multi-residential purchases are also more likely to involve a longer due diligence period, more detailed representations and warranties from the seller, and a purchase agreement negotiated specifically for the deal rather than a standard residential form. Your lawyer's role expands accordingly — coordinating with your lender's commercial underwriting requirements, reviewing existing leases and any assignable contracts (like property management or service agreements), and making sure the closing reflects the building's actual financial and legal condition, not just what's advertised.
Frequently asked questions
Why can't I get a regular residential mortgage on a 5-plus unit building?
Insured residential mortgage programs are generally designed around owner-occupied and small residential properties. Once a building reaches five or more units, lenders typically classify it as commercial or multi-residential and underwrite it differently, based on the building's income rather than primarily your personal finances.
Is a fourplex commercial or residential financing?
A fourplex (four units) generally still falls within the residential financing category in Ontario, while five units and up moves into commercial or multi-residential territory. The exact line matters, so confirm how your specific lender classifies the property before assuming either way.
Do I need a different kind of lawyer for a commercial apartment building purchase?
You need a lawyer comfortable with commercial real estate transactions — reviewing leases, financial due diligence, and commercial financing conditions is different work from a standard home purchase, even though many of the same closing mechanics apply.
What happens to existing tenants when I buy an apartment building?
Existing tenancies generally continue after a sale — as the new owner, you typically step into the landlord's role under the existing leases rather than starting fresh. Reviewing the leases and tenant files carefully before closing is essential to understand exactly what you're taking on.
Can my regular mortgage broker handle a 5-plus unit purchase?
Some can, but multi-residential and commercial financing is a specialized area, and not every broker who arranges residential mortgages regularly works with commercial lenders. Ask directly about their experience with buildings of this size before relying on their advice for financing structure.
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