The city inspects a secondary suite for a separate entrance in many cases, proper egress windows, adequate ceiling height and fire separation between units. A beautifully finished second unit that skipped that process still fails the test for legal secondary income, which affects both your financing and your resale value later.
Once legality is confirmed, get the actual rent history for the second unit rather than a projected figure, and have a lawyer review the title at ISC for any liens or easements before your conditions come off. A home inspection, typically $400 to $600, should cover both units, not just the primary residence.
Get your hand-reviewed valuation from Joel Dyck.