Up until a few years ago most people assumed that an offer was just that: an offer, not a contract. But in the McCarthy case (McCarthy v. Tobin, 429 Mass. 84, (1999), the Massachusetts Supreme Judicial Court held that a singed and accepted written offer that contains all material terms may be a binding contract. So, sometimes, even if a Purchase and Sale Agreement is never signed, the seller or the buyer can seek specific performance (forcing the other party to go through with the sale and purchase). As always, be sure you have the offer reviewed by an attorney and make sure you understand the nature of the document you are signing.