The Road to Hell is Paved With Hugh Jackman's Letter of Intent. There really is no benefit to seeking letters of intent from actors (or their reps). Producers hate asking for them, reps hate writing them, and financiers ignore them. They're usually out of date. They're not binding, nor are they conditional to anything that's relevant. And yet, they still rampantly persist within indie producing and packaging.
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.