i dont know about there, but i work in a gym myself. no im not a personal trainer, but what i do know is the salary is low (so ive been told, i myself was never told the actual number). BUUUTTTTT the trainers also get money from their clients ($50 per client, here anyways.) and each trainer gets clients daily.
pretty sure you already knew this, and this post might be completly useless to you.