What Is the 3-3-3 Rule for Buying a House? And Does It Work in Coquitlam?

Try the 3-3-3 calculator with your numbers ↓

What the 3-3-3 rule actually says

There is no official 3-3-3 rule. No regulator, lender or government publishes it. It is a budgeting shortcut that circulates on real estate blogs and social media, and it comes in at least two different versions.

Version 1: the 30/30/3 rule. This is the one most people mean. US real estate and banking sites describe it in three parts:

• 30% of income: monthly housing costs (mortgage, property tax, insurance and any HOA or strata fee) at or below 30% of gross monthly income.
• 30% saved: cash equal to 30% of the purchase price, meant to cover a 20% down payment plus about 10% for closing costs and an emergency buffer.
• 3 times income: a purchase price no higher than 3 times gross annual household income.

Version 2: the "three threes" of preparation. Other writers use 3-3-3 to mean three months of living expenses in emergency savings, about three months of mortgage payments held in reserve, and looking at at least three properties before you decide.

Both versions point at a real risk: buying a home you can get approved for but can't comfortably carry. The trouble is that the numbers were built for markets where prices are much lower relative to incomes than they are in Metro Vancouver.

Running the 30/30/3 rule on Coquitlam prices

Here is the rule applied to the Greater Vancouver REALTORS® MLS® Home Price Index benchmark prices for Coquitlam in September 2026. A benchmark is a "typical" home in the index, not an average sale or any specific listing; I explain how it works in what the MLS® HPI benchmark price means.

Very few first-time buyers in the Tri-Cities, or anywhere in Metro Vancouver, would pass that test, and many people who buy here successfully don't. That doesn't mean they are being reckless. It means the 3× figure doesn't describe how Canadian lending works or what this market costs.

How Canadian lenders actually decide what you can borrow

A Canadian lender doesn't multiply your income by three. It looks at two ratios and runs them at a stress-tested interest rate.

• Gross Debt Service (GDS): housing costs as a share of gross monthly income. CMHC's limit is 39%. Housing costs include mortgage principal and interest, property tax, heating, and strata fees (lenders commonly count half of the strata fee).
• Total Debt Service (TDS): housing costs plus every other debt payment (car loans and leases, credit cards, lines of credit). CMHC's limit is 44%.
• The stress test: for uninsured mortgages, OSFI's minimum qualifying rate is the greater of your contract rate plus 2% or 5.25%. Insured mortgages (less than 20% down) are qualified the same way. The ratios are calculated at that higher rate, even though you pay your actual contract rate.

The 39% ceiling on GDS is higher than the rule's 30%, and the stress test is stricter than it sounds. In my stress test guide I walk through why TDS, not GDS, is where most files actually get stuck.

Down payments work differently too. Canada's minimum is 5% on the first $500,000 and 10% on the portion above, up to $1,499,999. At $1.5 million and above, mortgage insurance isn't available and 20% is the minimum. The full tiers are in how much down payment you need in BC.

The same three homes, run the way a lender would

Here is a worked comparison for a buyer with no other debts, putting down the minimum, at the 4.44% lowest advertised 5-year fixed rate as of October 29, 2026 (Ratehub). The lowest advertised rates are often for insured mortgages. An uninsured mortgage, like the detached example, may be priced higher, which would raise the income needed.

Three things stand out. First, the lender's minimum income is well below what the 3× rule implies, because the rule assumes a much lower price-to-income ratio than Coquitlam has. Second, the "30% of income" part of the rule is actually stricter than the lender: keeping real carrying costs to 30% takes noticeably more income than qualifying does. Third, the detached column crosses $1.5 million, so the down payment jumps to 20% and the cash requirement changes completely.

That second point is the useful part of the rule. Being approved at 39% GDS means a lender will lend to you; it doesn't mean the payment leaves room for childcare, savings or a furnace replacement. I lay out every monthly line, including insurance, utilities and a maintenance reserve, in what a Coquitlam home really costs each month.

What about "30% saved"?

The rule's 30% assumes a 20% down payment. Most first-time buyers in Canada put down less and pay a mortgage insurance premium instead. What you actually need in cash on closing day is the down payment plus closing costs, and closing costs are mostly BC Property Transfer Tax.

So the 30% target is more than you strictly need to buy. But the minimum is also exactly that: a minimum. Buying with no cash left after closing is how the first year of ownership gets stressful. That is where the second version of the rule, the emergency and mortgage reserves, earns its place.

Run the 3-3-3 rule on your own numbers

Enter your household income, the cash you have and a price you are considering. The calculator shows what the 3-3-3 rule says, what a Canadian lender's stress test is likely to allow, and what the home would actually cost you each month, then gives the price a green, yellow or red light. It uses the same assumptions as the tables above, and nothing you type leaves your browser.

A BC version of the 3-3-3 check

If you like the idea of three simple tests, here is the version I find more useful for Tri-Cities buyers. It is a planning checklist to take into a conversation with your mortgage broker, not a lending rule or financial advice.

1. Three numbers from your lender, in writing. A pre-approval for your maximum price at the stress-tested rate, the actual monthly payment at your contract rate, and the payment if your rate were 2% higher at renewal. The gap between "approved" and "comfortable" is your real budget. Here is why a pre-approval beats a pre-qualification.
2. Three buckets of cash, kept separate. Your down payment, your closing costs (CMHC suggests planning for 1.5% to 4% of the price; in BC most of it is PTT), and a reserve after closing. The second version of the 3-3-3 rule suggests about three months of living expenses plus three months of mortgage payments, which is a reasonable starting point to discuss with your advisor.
3. Three recent comparable sales. Before you write an offer, look at at least three recent sales of genuinely similar homes nearby. The original rule's "look at three properties" is good advice, but comparing what similar homes actually sold for is what protects you from overpaying. I go through how in how to tell if a Coquitlam home is overpriced.

When I work with first-time buyers, the numbers come before the home tours, not after. I'll connect you with a Tri-Cities mortgage broker who can run your exact file, and I'll pull the comparable sales for any home you're serious about.

Where the 3-3-3 rule is still worth listening to

• If your price is above about 5 times your household income, look hard at the monthly carry and your other goals, even if a lender says yes.
• If your full monthly housing cost is above 30% of gross income, make sure you're choosing that on purpose: for a better location, a school catchment or room to grow, and with a reserve behind it.
• If closing would leave you with no savings, slow down. A delayed purchase is cheaper than a forced sale.

Use the 3-3-3 calculator above to compare the rule with the stress test on your own numbers, or the Coquitlam home affordability calculator for a fuller lender-style estimate with every debt type, and see how much home you can afford in Coquitlam for what different budgets buy.

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