Separate land use from building code
A province may broadly enable secondary units while a municipality still controls site-specific zoning standards. Building-code compliance is a second layer, not a substitute for zoning permission.
Decide the unit form early
An internal suite, basement suite, detached garden suite and laneway/coach house can have different height, setback, servicing and fire-safety requirements.
Build a paper trail
Keep zoning confirmation, plans, permits, trade approvals, inspection records and occupancy/registration documents. If buying an existing suite, ask for the file rather than assuming the current use proves legality.
Use the local library: find your city guide before treating a national article as the final rule.