First off, it is a horrible idea to put cameras anywhere inside the house. I would never in a million years stay in a place I found had cameras. Just the idea of someone watching you living in your temporary home is super-creepy. And if I ever caught someone filming me in a rental house/apartment without consent and prior notice... let's just say it would cause more trouble for them than any of their TVs or night-tables could be worth. Doesn't matter if it's a hall, living room, or common area - people have all sorts of habits they'd rather the world not know about. And if privacy is assumed, it should be private. If not, LET THEM KNOW!
Cameras on outside exits would be fine. Maybe even the outside of windows, but not with a view inside.
If you are allowed to and are going to put some cameras inside, PLEASE let them know on the advertizement. Not the night of - I mean on your advertizement page with the room numbers and amenities. First of all, letting them know already filters out most people with nefarious intentions. It also releases you from a lot of trouble if they find it out later - cause they agreed to stay already knowing. And finally, it's a risk for them staying in a strange house as well - the host could steal their stuff during the day, steal their identification info, or film them walking around the house naked.
Whatever the case, you want your guests to trust you and you want to be able to trust them. The best way to do this is by letting them know what's going on.
If you're paranoid, maybe let them know ahead of time that you need a copy of their ID and are willing to offer yours.