I’m not exactly sure, but I don’t think you really need to do anything besides ask them. It’s a good idea to do a quick background check on their criminal history, if they have one, just so you feel safe working with them.
The very least you should have contracts drawn up and have them read it and sign it before even setting foot inside the house. The contracts should have details on what’s expected of the students during the time they’ll be working for you and how much they’ll get paid, they agree not to sue you should they injure themselves while working under your supervision.
It’s best to have written and signed contracts for any business venture so there’s no disagreement or misunderstanding in the future between the parties. Everything is clearly outlined.