The City requires a building permit and inspection before a new suite counts as legal, covering things like egress windows, ceiling height and fire separation. Joel Dyck can tell you early whether a specific property is a realistic candidate before you spend money on drawings. Basement conversions are usually the more straightforward path in an existing house, since the foundation, roof and main services already exist, while adding a detached garden suite in the backyard means confirming setback distances and utility connections before a permit application even gets submitted.
Age and layout of the existing house matter too: older homes sometimes have ceiling height or window placement that does not meet current code without structural changes, which changes the cost math even when the zoning itself allows a suite.
The zoning question and the construction question are both worth answering before you commit to the idea. Get your hand-reviewed valuation from Joel Dyck.