There’s usually a difference between what you think you can afford and what a lender thanks you can afford. Lenders use two formulas to figure out how large a mortgage you can qualify for. Basically they add the monthly mortgage payment, property taxes, heat, 50 percent of the condo fees if applicable and divide the total by your pre-tax monthly income. If the result is less than .32 then your Gross Debt Service Ratio is fine.
They then determine your Total Debt Service Ratio by adding all the expenses listed above plus your monthly obligations for outstanding loans like car loans, credit card balances, etc. and divide that figure by your pre-tax monthly income. If the result is less than .40 then your Total Debt Service Ratio is fine. There is some leeway on these numbers depending on the lender, your credit score and whether the mortgage is insured or not.