I'd shoot for a EX500 to start out with: http://norfolk.craigslist.org/mcy/441796380.html

http://norfolk.craigslist.org/mcy/431102655.html

They hold their value quite nicely, unless you mess up the plastics or crash hard. I rode one for 7 months, bought a '99 F4 and rode it for 9 months, sold the F4, and I'm back to the EX500 as my track bike.

Plus, they're in your price range. You might be hard pressed to find a decent 600 for $2100. You'll also want to budget $400-$500 for good riding gear(helmet, gloves, boots, jacket).