Canadian mortgages compound semi-annually, which is different from the monthly compounding common in the United States, and that structure changes how quickly interest accrues over the life of the loan. Canada Mortgage and Housing Corporation guidelines also require lenders to apply a stress test that qualifies you at a rate higher than your actual contract rate, capping gross debt service at roughly 39 percent of income, so your approved amount is more conservative than the payment you would owe on day one.
For a buyer at Saskatoon's benchmark price of $444,700, even a modest rate move changes the monthly carrying cost enough to shift what neighbourhoods or property types stay in reach. Locking a pre-approval early in your search protects against a rate increase mid-search, though it does not protect against a decrease.
Talk to a mortgage broker before you set a budget, since the rate environment at the moment you are ready to buy matters more than what rates did a year ago. Get your hand-reviewed valuation from Joel Dyck.