Lenders decide much of this. When you buy a home with a legal secondary suite, mortgage default insurers including CMHC allow a portion of the documented rent to offset your carrying costs, which raises how much house you qualify for. An unpermitted suite gets no such treatment, and some lenders will insist the appraiser value the property as though the suite were not there at all. That single underwriting difference is what makes permits worth paying for.
There are costs on the other side of the ledger. Two units mean two kitchens, two sets of appliances, more wear, more insurance and, if you rent, obligations under The Residential Tenancies Act, 2006 covering notice, deposits and repairs. Some buyers pay a premium to avoid all of that, which is why a well kept single-family bungalow in a family neighbourhood can outsell a tired duplex nearby.
The premium also depends on where you are. Near the University of Saskatchewan and the older core neighbourhoods, rental demand is steady and suites carry real weight. In a newer suburban pocket, buyers are more often families who want the whole house. Joel Dyck values the suite on what it legally earns in that specific part of the city, then adds the conversion and upgrade work that public records never captured.
Get your hand-reviewed valuation from Joel Dyck.