Letters of intent may be advanced in the world of commercial real estate. In some specific domestic markets (for example in principal to principal deals between upstream Petroleum traders and producers in the same country, or certain Joint venture projects) they may be found. But there is no underlying and supported standard international application for the Letter of Intent.
Secret: Time is NEVER on your side when you are buying. Never forget that. Keep in mind that if you are looking to explore the viability of a purchase, a good starting point is the LOI. Once you get beyond the "overview" of what you and the seller are looking for, detail everything out in the purchase contract, and keep all of the above in mind when doing so.