Purchase offers usually aren't accepted as written. Commonly, buyers and sellers engage in the equivalent of a tennis match, counteroffering back and forth until they meet a mutually agreeable purchase contract. At this point, you might be inclined to think the negotiation phase of the transaction is over.
That may have been the case decades ago. But the home sale process has become more complicated over the years. Today, it might be more appropriate to say that the negotiations are over when the transaction closes. That is, if there aren't any after-closing issues, like a leaky roof that wasn't disclosed that could require more negotiation.