One of the most important things you can build into these documents is a clause that allows you to perform proper "due diligence" on the property. Basically you want to make sure that you have time to review all of the necessary financial information, management documents, and fully inspect the property itself BEFORE you finalize the purchase of the property. If things are not what they appear to be on the surface, it is better to find out now _ before you own the property than 6 months down the road.
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 They're usually out of date.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.