Permit status is the single most important check, because it decides whether a lender will count a unit's rental income at all. A unit that looks finished and rented in photos is worthless to your financing if the City of Saskatoon has no permit on file for it.
Rent documentation matters just as much as permit status. A seller's stated rent is a number until you see a signed lease and a payment history, so ask for both before you rely on any income projection in your offer or your financing application.
A home inspection, typically $400 to $600, should cover every unit in the building, and a lawyer should review title at ISC for liens or easements before your conditions come off. Get your hand-reviewed valuation from Joel Dyck.