LOI is used as manipulation tool at the hands of unscrupulous sellers & agents. Often times, obscure or scam_oriented persons who claim to be crude Sellers, or represent themselves as sellers' agents, mandates or brokers largely by an Internet contact or communication, employ the LOI merely as a tool to quickly "corner and box in" a prospective buyer to a purchase deal, before the prospective buyer may demand that they provide their business profile or show him something tangible to demonstrate that they are truly legitimate sellers.
One of the most important things you can build into these documents is a clause that allows you to perform proper "due diligence" on the property. Basically you want to make sure that you have time to review all of the necessary financial information, management documents, and fully inspect the property itself BEFORE you finalize the purchase of the property. If things are not what they appear to be on the surface, it is better to find out now _ before you own the property than 6 months down the road.