Question is in the title.

answer: as much as they want and are in demand for

Some trainers travel a lot to other barns and others don't travel at all if they have the facilities to train at home. Is this something you are considering doing yourself?

Working in a large chain health club is the starting point for many personal trainers. These large clubs are always hiring trainers. Working as a personal trainer in a large gym means that you will spend your entire day in the fitness center. Your duties will be to monitor clients to make sure they are using the equipment properly. You will often have some cleaning duties, as well. Some clubs allow you to train clients one-on-one during your shift, while others will require you to work with personal clients outside of your normal working hours. The upside is the benefits and steady employment; the downside is that your salary may be low, as you have limited time to do one-on-one training.