Cheap cameras can record to SD cards, so the network doesn't necessarily help. I'd say disconnecting the electricity would probably work, but makes it a bit hard to use the house, no?

My suggestion would be to assume you might be being filmed, rather than assume you can avoid it.

This sort of thing is an arms-race, and if you don't want to spend your life on counter-surveillance tech and opsec, you're not going to have any certainty.

Publicize, loudly, cases when someone violates your trust. Because that's what this reduces to; you're trusting whomever you're paying for that room. If they don't deserve that trust, ruin their income stream and they'll stop.

Applications of this approach to less-vulnerable violators left as an exercise, etc.