If the conversion was never permitted, the City of Saskatoon can require the work to be brought up to code or removed, and a lender or insurer may treat the unpermitted space as if it does not exist for financing purposes. That is the difference between a legal secondary suite and a basement that only looks like one.
Checking is straightforward: a property file search through the City of Saskatoon shows the permit history, and a lawyer reviewing title before closing, typically for $800 to $1,500, will flag an open or missing permit before you commit to the purchase.
An online listing photo cannot show you a permit number, and neither can an automated estimate. Get your hand-reviewed valuation from Joel Dyck.