yeah, get one, i got about 4-5 pocket bikes.. selling one this weekend for 400 bucks..
They are good fun, teach you heaps, if you get one the best thing you can get is a dremel, means you can mod it a heap for cheap.
port the carby, port the exhaust port, crank cases, snap off some of the flywheel fins, and stuff.. easy as to mod.
and they are pretty easy to maintain.