What the owner holds
The keys are only the visible part.
When a building changes hands, the keys fit easily into an envelope.
What passes with them is harder to contain. Someone knows which window sticks. Someone has opened the door every morning for twenty years. A neighbour expects the lights to come on.
A business also contains expectations that were never written into its sale.
People have arranged parts of their lives around its continued existence. Customers return because something familiar has been reliable. A name carries promises its new owner did not personally make.
Ownership does not require preserving every habit. It does require noticing what those habits have come to mean before changing them.
The transaction can establish who holds the keys. What happens afterwards establishes what kind of owner has arrived.