I'd be curious as to who would pay for your living expenses while you study, Jodo.
As for careers, here's my 2 cents, which may not be worth even that as my own experience is pretty limited:
I guess one of the first things I'd be asking is why do you want a career? What is it you expect to get from it? If it's simply to pay your bills or make money, I'd say that's probably easy enough - it's a job. The nice thing about a job you're only doing for money is that you can leave it behind when you go home. That's a big bonus.
But I'd say a 'career' is probably more than that. If it's something you want to devote time and mental energy to then I'd reiterate what Bamatone said - "something you love/like for less pay is much more rewarding and less stressful than doing something you hate for more money". In the real world, I guess we can't always do what we want - there just aren't enough champagne taster positions going. But that's no reason to stop striving to achieve your goals.
And I mean your goals. Not the goals that society tells you that you should be reaching for.
Aside from the reason Bamatone gave about basic satisfaction, there is another very good reason for this. Good jobs are pretty rare. Great jobs are even rarer. There are positions that people will never give up and they'd have to die to make a spot available. When they do, there will be hundreds of very talented people looking to fill that position. If you're really going to go for a career, you need to be good. Very good. And it's a hell of a lot easier to get good at something you love.
If you do that then, to answer your question, yes it's worth it. I'm doing it and it's worth it. Of course I still don't want to get up in the morning but probably even the pro-wrestlers are the same.
To answer your second question, I firmly believe that it's never too late to change career. So if you train or work your way up in a job and decide you don't like it, you can always retrain or move to a different job. You'll always build up skills that will benefit you. My mother took on a career in her late forties that she had never touched before and is now very successful. I have seen several people decide in their thirties to abandon what would be considered very successful careers to go back to college and study something they always wanted to do (usually following that pattern of less money but much more satisfaction). I dropped out of university myself early on realising that what I was doing just wasn't right for me.
If you find something you like now, I wouldn't worry about whether you'll like it in five or ten years. There's a very good chance you will change your mind at some point. That's cool. It's never too late to shift career.
My advice would be to aks yourself what you want to do. Not what you want to do from a conventional choice of accountant, lawyer or whatever. What you really want to do. Then start hunting for information. Some things don't even sound like real jobs but, scratch the surface, and you can be almost sure that someone, somewhere, is making a living from it.