I jacked in work at 23 went to uni to study business. I thought at the that time it would open lots of doors, it didn't. I landed in Financial Services, which I have a head for and the earning potential is high. I don't really need my Degree I am glad I have one but it was an unnecessary 3 years with no earnings.
I would say if you do decide to go for it, be specific about what you want to do, maybe pick something you enjoyed as a child but never pursued (or your parents were to stingy to pay for you to do). Find out what it takes to get hired doing that and then look into the courses or training you need to do it.