The overseer of banks in Canada is getting tough about making sure people buying homes can handle their mortgages.

Great, slack lending standards helped crash the U.S. housing market last decade. But the crackdown on mortgage lenders by the Office of the Superintendent of Financial Institutions won't address a big risk in housing today. This would be the finances of people after they buy, not before.

OSFI's requirements for lenders include more stringent verification of borrower income, more scrutiny of borrowers with low credit scores and tougher standards for checking whether borrowers can afford their mortgages if interest rates rise. These measures will help screen out marginal buyers who might default on mortgages, so they're welcome.

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But let's get real about home buying. Your finances are never in better shape than before you buy your first house. You've got your down payment money saved up (or given to you by mom and dad), you most likely have no kids, you've probably got your student loans paid off (please tell me you do) and you most certainly do not have a big balance on your home equity line of credit (you need a house to get one of these).

Lenders perform a pair of debt stress tests on you before you buy. One is the gross debt service ratio, or GDS, which is the percentage of gross monthly income needed to cover monthly mortgage, property tax and heating costs, plus 50 per cent of condo fees. Your GDS should not be higher than 32 per cent, according to Canada Mortgage and Housing Corp.

The other test is the total debt service ratio (TDS), which is the percentage of income needed to cover all the costs in the GDS plus other any other debt payments you have. GDS is supposed to top out at 40 per cent.

OSFI wants lenders to make sure borrowers can manage their debts both now and after rates rise. But we can take only limited comfort from this because higher rates are just an abstract risk. More worrying is the extra borrowing that many people do after buying a house.

Your TDS can turn into a pinata once you're a homeowner. The hits keep coming – a line of credit balance, a renovation loan, car loans, credit card bills that don't get paid in full every month. Suggestion to OSFI, the Bank of Canada, the Department of Finance, Statistics Canada or anyone else who gives a damn about the finances of the nation: Pay for a survey to check the total debt service ratio of people who have bought homes in the past three years, particularly in Toronto and Vancouver.

Even this added level of scrutiny wouldn't give us a full sense of the financial stress recent buyers are under. The biggest strain, especially in big cities, is daycare. Some parents call their daycare bill the second mortgage.

The value of knowing more about the debt loads of owners, as opposed to buyers, is that we would have a much better idea of how serious a problem household debt is. The most widely quoted debt gauge is the debt-to-disposable income ratio, which came in at 165.3 per cent in the first three months of this year.

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We've had screaming headlines about this ratio for so long that no one really cares any more. Anyway, it's a flawed measure because it mixes debt-free people with those who are in massive debt. The nuance of who's in the most trouble is lost.

A study of homeowner debt loads would be a sound basis for the federal government to consider measures to prevent the housing market from overheating. If we see people staggering under their debt loads after they buy, it might make sense to toughen standards before they purchase a house. We'd have fewer buyers, but they'd be financially solid.

The GDS and TDS are a good place to start with tougher borrowing standards. They've been around for decades and reflect a world where interest rates were higher and people were more cautious about borrowing. In many households, mortgages are only one slice of the debt pie today.

For this reason, we need to worry a little less about what rising rates will do to housing and focus on what low and still-falling rates have already done. It makes sense to limit how much debt people take on with a house in recognition of the borrowing to come.