Buying a Duplex in Ontario: Does the Second Unit Actually Cover the Mortgage?

The duplex pitch is compelling: buy a property, live in one unit, rent the other, and let the tenant help pay your mortgage. In theory it reduces your housing cost while building equity. In practice, the math does not always work the way the pitch implies.

This post runs the actual numbers on duplex buying in Ontario across different price points and markets, and shows you exactly what questions to ask before making an offer.

The Two Ways to Buy a Duplex

How you buy a duplex significantly changes the rules, the financing, and the numbers. For the full breakdown of minimum down payment requirements and closing costs in Ontario, see How Much Down Payment Do You Actually Need.

Owner-occupied purchase: You buy the duplex and live in one unit. Under this structure, you may qualify for a lower down payment since it is classified as your primary residence. You could potentially qualify with as little as 5% down on properties up to $500,000, or 5 to 10% on properties up to $999,999, subject to CMHC insurance rules. The rental income from the other unit can offset your mortgage qualification under many lenders' guidelines.

Pure investment purchase: You buy the duplex as an investment and rent both units. This requires a minimum 20% down payment as covered in the down payment rules for rental properties. CMHC insurance is not available.

The owner-occupied approach is significantly more capital-efficient but requires you to actually live there. If you are buying purely as an investment, the 20% minimum applies.

Real Numbers: Hamilton Duplex

A two-unit property in Hamilton at $699,000. Upper unit: $2,300/month. Lower unit: $2,100/month. Total monthly rent: $4,400.

Scenario A: Owner-occupied, 10% down

Down payment: $69,900
CMHC premium (3.1% on 90% LTV): $19,683 added to mortgage
Total mortgage: $648,783
Monthly payment at 4.5%, 25 years: approximately $3,547
Your unit cost: $3,547 - $2,100 (rental unit income) = $1,447/month effective housing cost
Compare to renting a comparable unit in Hamilton: approximately $1,800 to $2,200/month

In this scenario, buying the duplex costs you approximately $350 to $750 less per month than renting, while building equity. The math works.

Scenario B: Pure investment, 20% down

Down payment: $139,800
Mortgage: $559,200
Monthly payment at 4.5%, 25 years: approximately $3,057
Operating expenses (property tax $600, insurance $200, maintenance $550): $1,350/month
Total monthly costs: $4,407
Total monthly income at 5% vacancy: $4,400 x 0.95 = $4,180
Monthly cash flow: $4,180 - $4,407 = -$227/month

Slightly negative as a pure investment. The deal does not quite cash flow at these numbers, but it is close. A slightly lower purchase price, slightly higher rents, or a larger down payment would push it to neutral or positive.

Real Numbers: Toronto Duplex

The same analysis in Toronto changes significantly due to higher prices.

A two-unit property in Toronto at $1,100,000. Upper unit: $2,800/month. Lower unit: $2,400/month. Total: $5,200/month.

Pure investment, 20% down:

Down payment: $220,000
Mortgage: $880,000
Monthly payment at 4.5%, 25 years: approximately $4,810
Operating expenses: $1,600/month
Total monthly costs: $6,410
Monthly income at 5% vacancy: $4,940
Monthly cash flow: -$1,470/month

Deeply negative. At Toronto prices and current rates, a duplex purchased as a pure investment is unlikely to cash flow positively. The investment thesis in Toronto relies heavily on appreciation and equity buildup, not income.

What to Check Before Making an Offer

Four things to verify before you make any offer on a duplex in Ontario:

• Legal duplex status. Is the second unit legally registered and permitted? An illegal basement apartment creates liability issues, potential city orders to vacate, and financing complications. Ask the seller for building permits and verify with the municipality.
• Existing tenants and rent levels. If the units are tenanted, what are the current rents? Under Ontario's Residential Tenancies Act, rent increases for eligible units are subject to the annual provincial guideline. Units first occupied after November 15, 2018 are exempt from rent increase restrictions, though all other tenancy rules still apply. Confirm the status of any unit with a licensed paralegal or lawyer before making assumptions about rent control. If current rents are significantly below market, your cash flow analysis needs to use actual rents, not market rents.
• Separate meters. Are utilities on separate meters or shared? If you pay utilities for both units, your operating expenses are higher and your net income lower. Separately metered utilities typically increase property value and simplify management.
• Rental income for financing purposes. Ask your mortgage broker how much of the rental income your lender will count toward mortgage qualification. Different lenders use different methodologies. Some use 50%, others 80%, and some have specific rental income programs that use 100%.

The Break-Even Rent Check

Before modeling anything else, use the Break-Even Rent Calculator to find the minimum total rent needed to cover all costs at your financing terms.

Enter your monthly mortgage payment, property tax, insurance, maintenance, and vacancy rate. The calculator tells you the minimum monthly rent the property needs to generate to break even.

Compare that number to what both units actually rent for in the current market. If break-even rent is $4,800 and market rents are $4,400, the deal needs something to change before it makes sense as a pure investment. For a complete deal analysis framework, see How to Analyze a Rental Property in Canada.