Your profile is not filled in so I don’t know if you are certified with a Nationally Accredited Organization.
Being a certified trainer will allow you to have liability insurance which is a must.
As with all clients I would have them complete a Health History form, PAR Q, a personal training contract, a liability waiver, a medical release form from their doctor if needed, to name a few.
I would also do a very thorough pre workout interview and make sure to get everything is in writing.
I also suggest speaking to a lawyer and finding out what else you need to consider.