Go with the flow. Go over. Just keep your expectations low. You are not in his head so don`t know what he is thinking. I wiould consider all the possible outcomes and ramifications from them. Is he much younger or older than you? Is he just that comfortable in his skin, and means nothing by it, or is he curious. Can you have a one time fling if it goes there without any weirdness as you are neighbors? What if he gets emotionally wrapped up in you if you are his first gay experience? Are you prepared for that? Can you let him down gently if you don`t want that? Or reverse the senario.
Obviously only you can answer these questions, but if you are prepared for anything from nothing happening (save a case o blue balls) on your part, or an awkward aftermath on one or both parties parts, to a one time thing or ongoing, then go over and enjoy whatever he has to offer, be that his platonic company or a hot sweaty romp.