That tax point catches people out. Converting your principal residence to a rental is treated as a sale at fair market value on the date of the change, even though no money moves and nobody signs anything, and any gain to that point is generally sheltered by the principal residence exemption. From then on, appreciation is taxable. That makes a documented value on the changeover date genuinely important.
Then run the operating numbers honestly. Rent has to cover the mortgage, property taxes, insurance at landlord rates rather than owner occupied rates, utilities you are responsible for, maintenance and a vacancy allowance, with a reserve for the furnace and the roof. A tenancy runs under The Residential Tenancies Act, 2006, which sets deposits, notice periods, rent increase rules and a hearing process.
Financing changes too, since lenders treat a rental differently and refinancing is capped at 80 percent of value with no default insurance available. Compare the net rental return against what the equity would earn elsewhere before deciding. Joel Dyck's hand-reviewed valuation establishes the market number that both the tax calculation and the keep-or-sell comparison depend on.