Why the short-term door is closed for investment properties.
Toronto's rule is explicit: short-term rentals under 28 days are only permitted in your principal residence. The suburbs are less publicized but often stricter. Markham's comprehensive zoning bylaw does not permit short-term accommodations as-of-right in any zone — there is no licence to apply for, because there is no licence category. Enforcement is complaint-driven zoning enforcement, and a complaint can end the operation outright.
Owners sometimes read the absence of a registry as permission. It is the opposite. In a registration city like Toronto, the rules tell you how to operate. In a zoning city like Markham, the rules tell you that nightly rentals are not a permitted use at all. Neighbouring municipalities differ again — some currently have almost no STR-specific rules — which is exactly why a GTA owner needs to know their own city's bylaw, not the region's reputation.