The City of Saskatoon issues the permits that make a secondary suite legal, and that permit history is exactly what a future buyer's lawyer and lender will check, since an unpermitted suite can complicate financing and insurance even when the work itself is done well. Confirming zoning eligibility before you spend on construction is the step most homeowners skip and regret.
Financing the addition works differently depending on whether you plan to live in the house yourself. CMHC's insured lending framework allows a lower down payment, 5 percent on the portion of the price up to $500,000, for an owner-occupied property with a legal secondary suite, while a pure rental typically needs a larger down payment because the lender treats it as an investment property rather than your home.
Whether the cost of adding a legal suite actually pays for itself depends on your specific Haultain lot, the construction cost and what comparable suited homes have sold for, not a general rule. Get your hand-reviewed valuation from Joel Dyck.