Financing is the first step. A multi-unit property you will not fully occupy needs 20 percent down, and a lender will only count rent from units backed by signed leases, so gather every lease before you make an offer, not after.
Suite legality is the step buyers skip and regret. The City of Saskatoon requires each secondary suite to be permitted and inspected separately, and a three-family with only two legal suites is really a two-family for financing purposes, whatever the listing calls it.
The Residential Tenancies Act, 2006 governs every existing tenancy you would take on, including how much notice a tenant is owed if you plan to occupy a unit yourself. Get your hand-reviewed valuation from Joel Dyck.