Here are few factors that will determine the average profit margin:
-Mobile training vs. owning/renting a place
-The hourly rate you charge
-Other overhead expenses (equipment purchase, wear and tear of your vehicle, insurance costs, business expenses, etc.)
-Hours you are willing to work/week
-Individual training vs. group training
-Owning your own business vs. working for someone else
-Selling products other than personal training (supplements, etc.)
this cannot be answered with a single number because many factors influence the net profit.
A way to approach it is to look at your average monthly costs and compare it to the average income. The costs can vary widely between trainers and can be fixed or contingent on whether or not you train a client. Examples of fixed costs are leases for space and the utilities that go with it, liability insurance and potentially costs for employees. Variable costs would be transportation if you train at clients’ homes. Another aspect of cost is the equipment you purchase to train. Even though this expense is a one-time deal, it still should be pro-rated.