Traders are better off NOT using documents like LOI, ICPO, FCO, etc. Even if and when they rarely are used in internal trades, on a restricted level within specific industries, they have no legal or customary basis in International Trade whatsoever. In fact the presence of many of these terms are considered to be signs of Advance Fee Fraud, by knowledgeable players and law enforcement.
It is good to use an LOI to gauge the viability of purchasing the property based on the price an terms you are considering. IN other words, it is good to use to gauge whether or not the offer you have in mind is even going to come close to making sense to the seller.