The financing paths diverge too. An owner-occupant qualifies under CMHC's guideline of roughly 39 percent of gross income on housing costs and 44 percent on total debt, while an investor's application also has to account for a second property's carrying costs and, if there is a tenant, the Residential Tenancies Act, 2006.
A permitted secondary suite is worth more to an investor than an identical unpermitted one, because only permitted income can be underwritten by a lender, and that distinction matters just as much to an owner-occupant weighing whether to rent out a basement later.
Which buyer type you are changes the questions worth asking, not the need for an accurate number to start from. Get your hand-reviewed valuation from Joel Dyck.