If the letter of intent is accepted, then the due diligence period will begin. It will continue until the time agreed upon by both parties in which, at the end of the term, a binding contract is constructed. Terms may change during this time if certain aspects of a property, previously not disclosed, are discovered.
First my disclaimer. Laws vary from state to state and do change from time to time. This information should not be construed as legal advice. When you engage in any type of real estate or legal transaction, you should seek competent legal and real estate advice from a professional.