Legality is the single biggest swing factor. A secondary suite with a City of Saskatoon building permit, proper egress and a separate heat source is worth far more than an identical unpermitted unit, because only permitted income can be underwritten by a lender.
Public records and online estimates read square footage and lot size but cannot see whether the second suite is legal, whether a renovation happened without a permit, or what the actual rent roll supports.
That gap between what an algorithm sees and what is actually there is exactly what a hand-reviewed valuation closes. Get your hand-reviewed valuation from Joel Dyck.