Fun story http://www.cyclingnews.com/features/kyle-murphy-from-fixed-gears-to-summit-finishes/
He started as a junior, showing up at races and paying $5. All he needed was his helmet and a fix gear. At the OBRA run Alpenrose Velodrome.
OBRA has been all about making racing available to anyone who wants it. The track has its Wednesday beginer's nights where anyone can show up, pay a couple of bucks and get taught by some high caliber riders. At the annual Alpenrose Challenge, they have kiddie races after the lunch break.
The rider of this story left Oregon and OBRA long before he made any kind of a named for himself. But OBRA gave him a start. And that start was easy. Show up. You need a bike and a helmet. (And I am pretty certain he could have rented a bike. Hard up fpr cash but really want to try this? I bet a bike would find its way into that person's hands.)