We have a saying in our firm that smooth transactions make successful transitions. Basically, if two parties cannot agree on the elements of the LOI, they will probably have a hard time negotiating while dealing with the minutiae of the purchase agreement. Normally, once the key points of the deal are negotiated up front, the rest of the transaction tends to work much more smoothly.
Beware of an individual or group of people who call themselves Investment Bankers or a Buying Group. When they cannot provide you with personal financial statements or a financial statement from their company, you have a very slim chance of ever closing the transaction. The seller should have a copy of the financial statement from the buyer attached to all offers.