Legal, registered or just finished
Three things get called a basement apartment on a listing and only one of them is what the words suggest. A registered second unit has gone through the City of Pickering's process, reportedly including a building permit, inspections of the fire separation, exits and wiring, and an entry on the city's register; ask the seller to produce the registration and the permit file. A basement finished with a kitchen and a side door that was never permitted is common in the older streets south of the highway and in Liverpool, and it may be fine to live in but cannot be advertised or relied upon for income until it is brought into compliance, which can mean new windows, a fire-rated ceiling and a second exit. A rough-in or a separate entrance alone is a head start, nothing more. Price the work honestly, check the parking rules for a second unit, and have a lawyer confirm what the offer warrants.