Simple. If you have an outlet that provides you with clients, do it. If not, be prepared to grind. Most gyms have you sell training and will pay you nothing. With a certification taking a weekend and everyone doing it...best of luck making a decent wage. When anyone can be qualified to do something in 3 days for a $300 fee...expect $15hr.
If you're a private trainer and have a good hook up for clients....say you work at a bar, school with kid athletes, etc...if not, I'd say it's a waste. It's too over saturated a profession. The allusion trainers make $60hr working for a gym are way off. Private is the way to go, sure...but you need the clients.
It makes sense though. When anyone can do a job, it's worth less. Heart surgeon...there's a better call for a career. Supermarket bag boy, probably not as anyone can do it.
Lastly, I've noticed with training it has zero to do with how you look or even knowledge. If you are good with people and can sustain clients, you'll stay busy. Be sure to have them do pointless circuits and core ball bs, they'll think you're a genius and will actually need you to do the routine.
