Hi hamster...

The only thing that I would add to the already excellent suggestions is to listen to your instincts when talking to people.
Also there are free generic lease agreements online to copy and print out (make one for each of you). And require tenant insurance....they may not have much, but if anything happens they could hold you liable and not everyone is as honest as we are.

I would not expect anything if I was renting a room from anyone and I think that it's very nice that you offer....