It depends on where you train. If you live in the US, like I do, it depends on the sate board.

It depends if the therapist is an independent contractor or spa/clinic employee. 30% (+tips) is average when working at an establishment and the cost of the massage (-supplies) when working independently. So, as you can see, it varies greatly.

They make around $32.60 an hour. Massage therapists work long hours on their feet and it is an extremely physically demanding job. They make more at times from tips.

The possessive is a normal singuar possessive, therapist's (of, about, or belonging to one therapist).

Well a message therapist uses messages to help you and a physical therapist uses physical exercises to help you.