The entire process of making an offer involves negotiation. You purchase a home at a certain price for specified terms, including contingencies that allow you to back out in certain circumstances. The sellers read you offer and then either accept or, more likely, counter at a different price and with different terms, perhaps eliminating some of your contingencies and modifying others by limiting them for example, in terms of time. Thus the sellers may agree that you can have an inspection, but you must approve the report within, say, 14 days.