On Offer acceptance there is either a contract generated or a pro forma invoice generated. Since the offer is binding once accepted, the offer if well enough detailed and advised can and often does take the place of the contract. Customarily in Real Estate transactions the purchase offer itself is generally also the contract for purchase as well. The offer becomes a binding contract once accepted.
"Letters of Intent, legally, are the worst of all worlds. Writing a letter of intent is not to be taken lightly. In law, you either have a contract or you don't. LOI's are the legal equivalent of "almost pregnant." Letters of Intent emphatically state that. They state that they are not formal agreements, and then often proceed to set forth agreed terms of the proposed transaction. Given this paradox, if the deal goes sour, one party can argue [in court] that those agreed_upon points were, in fact, agreed upon _ or, in fact, a binding contract. And, in some cases, furthermore, that the party relied on the LOI and has monetary damages based on such reliance."