Condition removal is usually the first milestone. A buyer's financing approval and a home inspection, typically $400 to $600, both need to clear within the timelines written into the offer, and either one falling through can send the deal back to the market.
Once conditions are removed, both lawyers exchange the documents needed to register the transfer, including the mortgage discharge on the seller's side, and Information Services Corporation processes the actual change of title on or before the agreed possession date.
Possession day is when keys and legal ownership actually change hands, not the day the offer was signed. Get your hand-reviewed valuation from Joel Dyck.