We have a renter that has stayed in one of our available Airbnb rooms almost since we started renting it. He left once, gave us a good review, and came back a few days later. Just when his contract is about to expire, he extends it; sometimes by a day, or by several days. He always pays his rent. The property's out of state but I've been there when he's there, I met and chatted with him, and he's very quiet, clean, and respectful. We appreciate the reliable income, but this seems unusual. I glanced at his laptop and it appeared older and small, so I'm not sure he's actually working in there; we don't smell smoke, for example, so we've let it go. But should we be concerned?