The City of Saskatoon's zoning bylaw sets out which residential zones allow a legal secondary suite, and older neighbourhoods near downtown were platted before the single-family suburban model became the norm, so many of those lots already carry zoning that supports a second unit. Newer developing neighbourhoods are typically zoned and covenanted for single-family use from the outset.
Financing an income property also runs easier when the secondary suite is legal and permitted, since a lender will only credit rental income toward qualifying when the unit is documented properly and the debt service ratios, capped around 39 percent of gross income under CMHC guidelines, still work. An unpermitted suite in an older home can still rent, but it complicates both the mortgage approval and the eventual resale.
Confirming zoning and permit status on a specific address before you make an offer beats assuming an older neighbourhood automatically allows what you have planned. Get your hand-reviewed valuation from Joel Dyck.