I was a market maker on the London Stock Exchange for 5 years in the 90's.
I loved and hated my job. I left in 1999, and trained at OATS. I was 25.
I did OK at OATS and got a place on the CTC/ATP scheme. I joined jmc straight on the 757. I had an 18 month "career break" at DHL Air, and returned recently to Thomas Cook Airlines UK to fly an A320.
I am lucky, I know that. I got a big break early on and am grateful for it. I am also lucky to be in a final salary pension scheme etc etc.
However, the job has changed and is changing more still. The loco's have changed it FOREVER combined with 9/11. And it is not for the better. See above comment about pension etc... they are gone forever too now generally.
My advice is : If you LOVE flying, then do it. If it is a whim, don't bother.
I imagine I am in a lucky minority, however not alone in my luck, so if you work hard and commit to your studies then you may get lucky too.
All the best.