Mortgage Basics: Principal, Interest, and Amortisation
A mortgage is a secured loan where the property itself serves as collateral. Every monthly payment is split between interest (the cost of borrowing) and principal (repayment of the loan balance). In the early years of an amortisation schedule, the vast majority of each payment is interest — on a 25-year Canadian mortgage at 5%, roughly 75% of your first payment goes to interest. This ratio shifts over time as the principal balance declines: by year 20, most of each payment is principal. This front-loading of interest is why refinancing resets the clock and can substantially increase lifetime interest costs even when your new rate is lower.
Amortisation is the total period over which the loan is fully repaid. In Canada, insured mortgages are capped at 25 years (or 30 years for first-time buyers purchasing newly built homes under recent rule changes); uninsured mortgages can go to 30 years with most lenders. In the US, the standard is 30 years for conventional conforming loans, with 15-year and 20-year options widely available. Longer amortisation periods lower monthly payments but dramatically increase total interest paid. A $400,000 mortgage at 5% costs roughly $85,000 more in total interest over 30 years versus 25 years.
The term is different from the amortisation period. In Canada, terms are typically 1–5 years (with the mortgage then renewing at prevailing market rates), while in the US the standard is a 30-year fixed rate that does not renew — the rate is locked for the life of the loan. This distinction has profound implications: Canadian borrowers bear renewal risk (exposure to higher rates at renewal), while US borrowers who locked in low rates in 2020–2021 continue to benefit from those rates regardless of what the market has done since.
Canadian vs US Mortgages: Key Structural Differences
The most technically important difference between Canadian and US mortgages is compounding frequency. Canadian mortgages compound semi-annually (twice per year), while US mortgages compound monthly. This means the effective annual rate on a Canadian mortgage is slightly lower than a US mortgage with the same stated rate — the difference narrows to near zero at low rates but becomes material at higher rates. Financial calculators that do not account for this distinction will produce incorrect payment figures for Canadian mortgages.
Mortgage default insurance operates differently in both countries. In Canada, CMHC (Canada Mortgage and Housing Corporation) — along with private insurers Sagen and Canada Guaranty — provides high-ratio mortgage insurance for loans with less than 20% down on owner-occupied properties. The premium (0.6–4% of the loan amount, depending on LTV) is added to the mortgage principal and amortised over the loan life. CMHC-insured mortgages are not available for investment properties without owner-occupancy. In the United States, PMI (private mortgage insurance) is required on conventional loans with less than 20% down and is paid as a monthly premium that can be cancelled once equity reaches 20%.
Canada's mortgage stress test requires borrowers to qualify at the higher of their contract rate plus 2% or the Bank of Canada's minimum qualifying rate (currently 5.25%). This test effectively reduces how much you can borrow and is one of the primary reasons Canadian investors with multiple properties often find it difficult to qualify for additional financing using traditional lenders. The US has no equivalent universal stress test, though individual lenders apply their own underwriting standards.
Qualifying for an Investment Property Mortgage
Lenders assess affordability using two key debt ratios for Canadian residential mortgages. The Gross Debt Service (GDS) ratio measures housing costs (mortgage principal and interest, property taxes, heat, and 50% of condo fees) as a percentage of gross income — the maximum is 39% for insured loans, with some lenders allowing up to 44% for uninsured. The Total Debt Service (TDS) ratio adds all other debt obligations (car payments, credit cards, student loans, other mortgages) to the numerator — the limit is 44–50% depending on the lender and product.
For investment properties, rental income treatment varies significantly between lenders. Some lenders apply an offset method (adding 50–80% of rental income to your income), while others use an add-back method or apply the full NOI. The most flexible rental property financing in Canada often comes from B-lenders or credit unions that apply more liberal rental income offsets, though at higher rates. In the US, rental income from investment properties is typically treated at 75% of market rents for qualifying purposes, with the remaining 25% assumed to cover vacancy and expenses.
Credit score requirements are higher for investment properties than primary residences in both markets. Most Canadian major bank lenders require a minimum score of 680 for investment financing; US conventional lenders typically require 640–700+ depending on the LTV and number of properties. Each investment property mortgage typically adds to your reported liabilities, progressively reducing your qualifying capacity for subsequent properties — investors building portfolios of 5+ properties often find they need to transition from conventional bank financing to portfolio or commercial lenders that underwrite on asset quality and DSCR rather than personal income.
Refinancing: Break-Even, HELOCs, and Cash-Out
Refinancing can serve several purposes for real estate investors: securing a lower rate, accessing equity through a cash-out or HELOC, extending the amortisation to improve cash flow, or switching from a variable to fixed rate. The break-even analysis on a rate-driven refinance is straightforward: divide the total transaction costs (penalty, legal fees, appraisal, discharge fees) by the monthly savings from the new rate. If closing costs total $6,000 and the new payment saves $200 per month, break-even is 30 months — only worth doing if you plan to hold the property for at least 2.5 years.
In Canada, breaking a fixed-rate mortgage before term triggers an Interest Rate Differential (IRD) penalty, which can be substantial when market rates are significantly below your contract rate. Variable-rate mortgages typically carry a simpler 3-month interest penalty. Many sophisticated Canadian investors deliberately choose shorter terms or variable rates to preserve refinance flexibility, accepting somewhat higher rates in exchange for reduced prepayment penalties.
A Home Equity Line of Credit (HELOC) against an existing investment property or primary residence is a popular tool for funding down payments on additional properties. HELOCs are revolving credit secured against equity — you draw what you need, repay it, and redraw as opportunities arise. In Canada, you can borrow up to 65% of property value via standalone HELOC (or up to 80% combined with a mortgage through a readvanceable product). The interest is generally tax-deductible when the funds are used for income-producing investments, which makes HELOCs an efficient tool for acquisition financing when properly documented.
Fixed vs Variable Rates: Trade-Offs for Investors
The fixed vs variable debate has no permanent winner — the optimal choice depends on your risk tolerance, holding period, and the current shape of the yield curve. Fixed rates provide payment certainty: you know exactly what your debt service costs will be for the entire term, which simplifies cash flow projections and hedges against rate spikes. Variable rates (in Canada, these track the Bank of Canada overnight rate via the prime rate) historically deliver lower average rates over time, but require tolerance for payment fluctuations.
Over long holding periods, academic and empirical evidence consistently shows variable-rate mortgages have outperformed fixed rates in most environments. A frequently cited Canadian study found variable-rate borrowers paid less interest roughly 90% of the time over multi-decade periods. However, the 2022–2023 rate cycle — where the Bank of Canada raised rates by 475 basis points in less than 18 months — was one of those 10% scenarios, leaving variable-rate borrowers paying significantly more than those who locked in at pre-hike fixed rates.
For investment properties specifically, the penalty cost of breaking a fixed mortgage often looms larger than for owner-occupied homes, since portfolio restructuring, property sales, and refinancing are more frequent. Many experienced Canadian investors gravitate toward 1–3 year fixed terms or variable rate mortgages to preserve flexibility, accepting the renewal risk as preferable to a large IRD penalty blocking a portfolio transaction. US investors with 30-year fixed-rate mortgages face this less acutely — once locked in, there is no renewal risk, and you can always refinance if rates drop materially.