At the end you should sign off with "sincerely yours" or any other related salutation. If you are writing a letter of intent for graduate school then it would have a different content. First of all letter of intent would start with your name, address, contact number and email address. After you have mentioned the date, you should then add a salutation like "Dear Sir/Mam".
The point is that the often_heard notion and claims by some sellers or their overzealous agents and brokers that the use of the LOI to initiate a purchasing proposal by a buyer "is how it is usually done and this is how it should be," may be applicable and prudent only in the minds, the imagination, and hopes or dreams of those sellers, especially the more marginal ones and their brokers and agents who operate on the fringes largely on the Internet. It is NOT a view that is shared by the broad spectrum of credible buyers, more especially when the "sellers" involved are largely unknown and obscure operators.