How living in one duplex unit changes the loan

Buying a duplex and living in one of the units is usually underwritten as an owner-occupied home, not as a rental building you never sleep in. That occupancy is what opens the lower down-payment product and lets more of the second unit's rent count toward qualification. Rent does not cancel the mortgage payment. It changes the income side of the ratios.

Occupancy picks the product, not the number of doors

Two units under one roof do not, by themselves, tell a lender which rules apply. The deciding fact is who will live in one of those units after closing. CMHC Purchase is built for a home intended for owner occupancy: the borrower, or a spouse, common-law partner, or parent or child who lives there rent-free. At least one unit has to be occupied that way.

If nobody lives there, the file leaves that product. CMHC then treats it as a small rental property that is not owner-occupied: a 20% minimum down payment, a maximum loan-to-value of 80%, and a purchase price under $1 million. Rent still counts, but under a tighter method.

Occupancy is not a vague plan. The lender may ask for proof of address, an occupancy declaration, or home-insurance documents. Calling the duplex a principal residence while both units will be rented changes the product and the ratios. If you will not live there, say so before anyone prices the down payment.

Down payment follows occupancy, then unit count

For a one- or two-unit owner-occupied property that qualifies for insurance, CMHC uses the same equity rule as for a single house: 5% of the first $500,000 of lending value and 10% of the rest. An owner-occupied three- or four-unit building needs 10% of the whole value. The purchase price or lending value has to stay under $1.5 million for this product. The maximum amortization shown is 25 years.

Those figures are the minimum equity, not the full cash you need at closing. Notary fees, inspection, appraisal, transfer tax and moving costs still sit beside the down payment, as our guide to down payment and cash to close explains. A reserve after closing matters more here than with a single-family home: a vacant rental, a failed water heater, or a damage deposit to administer tends to arrive early.

If the down payment reaches 20%, mortgage insurance is no longer required for a conventional ratio. Waiting for that threshold is not automatically wiser: the extra cash may be more useful if the tenant leaves. Without occupancy, 20% is not a preference. On a $520,000 purchase, the insured minimum is $27,000 if you live in one unit and $104,000 if you do not.

How the other unit's rent enters the ratios

The mortgage payment, property tax and heat sit on the whole building. Employment income does not rise because there is a second door. Rent is used to widen the denominator. CMHC's GDS and TDS page says that for a two-unit owner-occupied property it will consider up to 100% of the gross rental income from the secondary suite. For other properties that are the subject of the insurance application, the usual cap is 50% of gross rent, and taxes and heat may then be left out of the ratios.

Up to 100% does not mean every dollar collected becomes eligible income. The lender works from a lease, a rent history, or a market estimate if the unit is empty. A listing that is high for the street, a long vacancy, or a below-market lease to a relative is documented differently. The method in use may also drop taxes and heat from the ratios, or put them back in.

The caps themselves stay where they are: GDS of 39% and TDS of 44% on the same page. They are calculated at the qualifying rate, the greater of the contract rate plus 2% and 5.25%. Our article on the mortgage stress test walks through that rate choice. For a duplex, the distinctive lever is the income add-back, not the floor-rate formula.

The gross rent used to qualify is not the net rental income on a tax return. The Canada Revenue Agency explains how to calculate rental income after expenses. A file can pass with $1,350 of gross monthly rent while, after costs, repairs and tax, the real surplus is much thinner.

A worked example: rent helps, then the file still fails

Suppose a household earns $95,000 a year before tax, about $7,917 a month, with $300 of other monthly debts. It is looking at a $520,000 duplex and will occupy one unit. The other is leased at $1,350 a month. Property tax is $400 a month and heat is $180.

The insured minimum down payment is $27,000: 5% of $500,000 plus 10% of $20,000. The loan before the premium is $493,000. At that loan-to-value, the owner-occupied insurance premium in the 90.01% to 95% band is 4.00%, about $19,720 if it is added to the mortgage. The insured balance becomes about $512,720. That is not an offer. It is arithmetic to show the mechanism.

Use an illustrative contract rate of 4.50%. The real monthly payment, with ordinary Canadian compounding and a 25-year amortization, would be about $2,840. The stress test uses 6.50%. The qualifying payment then rises to about $3,430.

With no rent at all, tested housing costs including tax and heat exceed $4,000 a month, more than 50% of employment income. The file fails. Add up to 100% of gross rent to income, and if tax and heat are excluded under the gross-rental approach, GDS falls to about 37% and TDS to about 40%, under the 39% and 44% caps. If the lender puts tax and heat back into housing costs, GDS rises to about 43% and the file crosses 39% again, even with $1,350 of rent.

The same household chasing $580,000, with $1,400 of rent, stays above the caps even if 100% of gross rent is used: GDS then sits near 46%. That project is not almost there. It needs a lower price, higher income, more equity, or less non-housing debt.

Gross rent is not cash in the account

Even when the ratios pass, the full real payment is still due the month a unit sits empty. In the $520,000 example, about $2,840 of principal and interest plus tax and heat is more than $3,400 a month. Subtract $1,350 of rent and more than $2,000 still has to come from employment income. Two vacant months, a roof repair, or a jump in insurance can swallow a year's surplus.

Québécois rental rules, delays to repossess a unit, and limits on rent increases are not part of the GDS formula. They decide whether that $1,350 will still be there. A sitting tenant paying below market lowers the income the lender can use, even if a nearby listing shows more. An empty unit forces an estimate, and that estimate can be lower than the rent you hope to charge.

Landlord insurance costs more than a simple single-family policy. Those premiums do not always enter the qualification math. They do enter the bank account. A duplex also takes time: showings, repairs, collection. That is the work of being a landlord, even with one door.

When the product flips, and what to line up

Owner-occupied financing collapses if the second unit is not a dwelling the lender and insurer will recognize: no separate entrance, no full kitchen, no permit, or no municipal compliance. The appraisal may then treat the building as a house with a finished basement and no eligible rent. Paying a duplex price does not create duplex status.

The product also flips if the promised occupancy never happens, or if you later move out and rent both units. A later refinance can then follow rental-property rules: more equity, a different premium, a lower price cap. That is not a reason to invent occupancy. It is a reason to pick the right product before the offer.

Before you tour, line up four facts rather than a target price. Confirm who will occupy which unit. Get the current lease or a documented basis for rent. Separate the down payment, closing costs and a vacancy reserve. Then calculate the payment at the qualifying rate, with and without the rent.

I match those pieces to documents rather than to a listing. The point is to see whether the plan works because you live in one unit, or only if an optimistic rent arrives on time. You can start a prequalification to test those scenarios before an offer. A first conversation is free and does not commit you to a lender.

Certain conditions may apply. Subject to change without notice.