I don't think that really answers the question. There will evidently be questions that require the owner's actual interaction. (Eg. Q: which light switch controls the outdoor lights; how much water do I give your plant?). The only thing I can think of is getting some information beforehand from the owner (which at that point may as well be given to the renter).

This solution is great for general area questions, but guests will likely still have specific questions about the actual building they are in (how do I turn on the hot water, etc). How will you deal with that?

Edit: Koby's response just popped up as I was composing this; I like the idea of learning from previous responses!