I agree with you that he had to know the area, at least in a general,sense, where the quiet roads are, stuff like that. Come to think of it, I grew up in a spread out area, heavily wooded, not rural but rural parts. In high school I knew all the side roads, back roads, the roads few people traveled, or cops rarely went...why? Teenage stuff...woods parties, parking spots, spots to go smoke marijuana. If JLM grew up around here, its possible he could have been familiar with the area for similar reasons.
Also I just wanted to point out that where HG was found it wasn't really abandoned property. It just wasnt currently being occupied. It was owned, on the market for a bit even, and was trying to be rented. To me abandon building is like one that's run down, and no one claims, or is caring for. This was t me a propert, without current residence. Anyway the simple semantics, change to me, what JLM would have known about that location, and perhaps more importantly why he would have known about that location. Its not like he knew of an old, long since abandon property no one goes too. This house was different then that. He would have specifically have to have known, that no one was CURRENTLY living there. It strikes me that it simply wouldn't have been enough to have seen the house listed on rental, or on a for sale sight, and know it wasn't being occupied. Because plenty of places for sale or rent still have current tenants. Perhaps he visited with the landlord and knew no one was there? I dunno that seems also too premeditated for this guy. I'm not convinced he was a planner, beyond strike when there was an opportunity, and he had a "hunger" (which seems stronger in the fall btw). More likely I'd be willing to bet he had a conversation in the days and weeks before at some point about that very house, and someone mentioned they were trying to rent it, but no one was living there, in a casual conversation way. Then when he had HG and started driving, he thought of that place.