So, I have to do the work for you to prove that (1) the fitness industry attracts a considerable amount of money and (2) that there are industries that deal with lower amounts of money. Most people would consider this a trivial point, not really worth discussing, but you think it's some type of grand mystery that has anything to do with your hero being clairvoyant.
So, here goes. Find a general listing of the general value of industries
here. They are arranged by NAICS codes (what the US government uses to abbreviate industries for organizational purposes). Now, all you need is find out the specific industries contained in each NAICS classification, right? Go
here for that. Just in case, you're too lazy to do the legwork, the NAICS code you're looking for is 713940. Maybe you want me to read it to you as well?