Search for "personal trainer outlook handbook" and click on the first link that comes up (since I can't post it yet)
It's from the Occupational Outlook Handbook
My dad is a trainer, but is not his own boss - he works at the YMCA. So 3 days every week he works just doing basic things, like making sure people are using machines correctly and restocking materials. On the side, he has appointments throughout the week doing evaluations and training sessions with YMCA clients. Then, twice a week he teaches a spinning class. But a place like the Y has its own requirements, so I imagine that going solo is very different.