Do I get the keys the same day the money changes hands, or is there a delay?

Ordinarily, yes — possession is meant to happen the same day funds are released, and lawyers on both sides generally coordinate the exchange so the buyer isn't paying without also getting possession, and the seller isn't handing over the business without being paid. That simultaneous exchange is one of the main things the closing process is designed to protect.

In practice, a short same-day gap can still happen for purely logistical reasons — the seller needs a few hours to finish clearing out personal items, or the funds transfer completes later in the day than expected — but this is meant to be hours, not days. If the purchase agreement specifically calls for a delayed possession date after the money changes hands (sometimes negotiated so the seller can wind down operations, for example), that's a deliberately built-in term, not something that happens by default. If your agreement is silent on this and you expect same-day possession, confirm that expectation with your lawyer before closing day arrives.