I was into mtn mikes when I was kid, been needing to get another one, mine got stolen.
The thing to look for in a bike as far as quality aside from what brakes, and weight, etc., is the welds. Look for nice smooth welds with no holes, especially on the inside radius of the joints. No lumps and sloppy bumps.
Audio production is fun. You could also buy a guitar and a Tab book and learn something you can do the rest of your life.
I few months ago I got a Bearded Dragon, about $500 for setup and dragon. He's a foot long now and I'll need a bigger tank soon.
http://i337.photobucket.com/albums/n361/OpticWaves/Vern/Image000.jpg