Ditto what Sharon said...I'm also a PT Assistant, and when in massage school (and pregnant no less) they worked my fingers to the bone! Bear in mind that they will expect less effleurage and more friction and deep tissue in very specific areas. It is much harder on your hands than the typical massage work.
As for what they pay you - I would ask what they bill per unit (most of your work will be in the 10-20 minute range per patient is my guess) and then figure a perceneforum.xxxe like a 40/60 split. They may not go for that, but see if they'll do a per diem rate for your actual massage work. One thing to consider is if you're being paid for the time you're not doing massage, and what sort of tasks you'll be asked to do. Laundry, cleaning, filing or whatever. If they're paying you by the hour, they'll want to keep you busy doing massage as much as possible - and that may not be very sustainable for your body over time.
IME, many clinics use massage as a real "bread and butter" kind of billing. Clients love it, the owners can pay an aide or assistant (or a MT) a low wage and charge a high rate. It can be pretty out of balance.
Good luck!