Legal status decides most of the gap between two similar-looking properties. A lender will only credit rental income from a unit the City of Saskatoon has permitted, so an unpermitted third unit contributes almost nothing to the appraised value even if it is fully finished and currently rented.
Expenses matter as much as income: property taxes, insurance, utilities not covered by tenants and a realistic vacancy allowance all come off gross rent before you get to a number a lender will actually underwrite, and a seller who only quotes gross rent is showing half the picture.
The Residential Tenancies Act, 2006 governs any existing leases and transfers with the sale, so those need reviewing before a price is finalized. Get your hand-reviewed valuation from Joel Dyck.