The usual rule for figuring out the size of your mortgage payments versus you income is a maximum of 32% of your gross income for taxes, heating, mortgage payments and ½ your condo fees (if applicable). A maximum of 40% of your gross income is used if you have additional debt payments. The percentages are known as the GDS and TDS ratios and aren’t cut in stone, there is usually a bit of wiggle room.
Here’s a great calculator for GDS and TDS. CMHC debt service calculator
Once you know how big a mortgage payment you can have, you need to use that number to calculate your maximum mortgage size. Play around with the numbers because rates, amortization and other factors greatly affect the result
Here’s a great mortgage calculator: Scotia mortgage payment calculator