Jake, it's like any other industry. You name the industry, ...especially one that spawns a huge cottage industry, ...and only that top tier will ever make any "REAL" money, ...but at the same time, many will be able to make a living, while others will barely be able to keep their heads afloat, ...and many others still unable to make ends meet.
Everyone's goals are different. Not everyone wants to break the bank. For some... making a living doing something they love is all they want or need to be happy. And if and when they do, ...they are successful, ...more so than many others making 20 - 100 X's as much money, ...but hating everything they have to do to earn that money.
Think about it, ...a doctor probably makes more than a poet, but if that poet can put a roof over his head, food on his table etc., he probably enjoys his life more so than the proctologist making a 6 figure annual income, but who has to constantly stick his fingers up other people's big fat hairy butts to do it. Just a little food for thought. 
Yes Yes Yes - But...
I personally see the Gym/ fitness field as a VERY tough one to pull a profit. (esp in the USA)
I'm not Trump, but I know what I'm looking @ re:Business.
I been around, and Bar/ Restaurant and the Gym thing are similar in the type of people/reason they open IMO.
The number of naive folks that go in w/ their heart is staggering....
It damn well better be money and time they can burn IMO (unless they were born into it, and grew up around it)
because odds of failure are better than not.
I dont want to ruin anyones "Dream" but I dont want to see them living a nightmare. And thets exactly what most get.
The number of Foreigners thinking of opening a Bar/restrant in my wife's country are high. Many try, few last long.
They call on the phone and talk to her thinking they can swing it w/ $20-$50K

They'd be better off taking that money to Vegas.
I could prolly pull off a small gym that would be worth the trouble in her country, but it would not make tons of money. Is that a smart idea? Not for me, right now.
When you go at a venture, you plan your best to succeed, but there must be contingency for failure.
Without prior Biz experience anyone is better off involving self in ANY kind of Biz for years before making the leap to
ownership. Ive seen so many fail, even in trades they were born into and expert at.
Maturity and experience are the only hope of success.