Fairhaven is a quieter, established Saskatoon neighbourhood, so a two-family purchase there is more likely to be an older conversion than new construction, which raises the odds that the suite predates current permit requirements. That is not disqualifying, but it means confirming permit status is the first call to make, not the last.
Beyond the mortgage math, a landlord is taking on the Residential Tenancies Act's rules on notice periods, deposits and repairs, plus ongoing maintenance on a second kitchen and bathroom. Budget a $400 to $600 inspection on both units before you close, since a problem in the rental unit costs you tenant relations, not just repair money.
Run the numbers on documented income, not asking rent. Get your hand-reviewed valuation from Joel Dyck.