I got my own computer when I was a teenager. Before then, it was just using my brother's Macs - I have fond memories of his Apple //e and SE/30. I started off with PCs (a 200 MHz Pentium II, I believe), built my own, etc., and then bought my very own Mac 2 years ago.
ive had hand down computers since i was about 7. my latest is my dads old PB in my sig. but im gunna buy my first new computer in January hopefully! but my brother is paying half!! i still have the old ones 8 in fact:
Mac Classic 2
LC 475 (ive got 2 of them)
Powerbook 233Mhz (OS 9)
Powerbook 400Mhz current on in sig
my last computer was a Blueberry iBook 300Mhz (no firewire) but i gave that one to my sister!
when my dad got his new iBook 1.2Ghz he gave my sister a choice of the Powerbook 400Mhz or my old iBook and me get the Powerbook. she asked for the blueberry iBook 'cos it looks cute' all she uses it for is to sync her pink iPod mini to it... oh well i'm not complaining!
I'm not in that age group anymore, but I got my own computer when I turned 16 because that's when I started taking AP English courses. I had so many papers to write that it started to get hard juggling time for my whole family to use the computer. I got my laptop when I left for college, since my desktop wasn't practical for a dorm room and the library. My brother got his frist computer when he turned 14, but it was one of those four hundred dollar Dells.