At that price, go for an 89 944 Turbo or Turbo S. Ridiculously fast and great handling in stock form. And they can be tweaked to go alot faster (as well as handle better) for not alot of money. You're looking at a very old 911 in the $15K range, and the older 911s aren't the greatest cars in the world, especially from a realiability point of view.
The 944 is often scoffed at as a "fake" Porsche, but come to a PCA event, and you'll see ALOT of 944s on the track (many of these 911 owners who have 944s as their track cars), putting down consistantly faster numbers than alot of 911s. They're great cars that aren't as expensive as 911s to fix, and they are plentiful, hence the cheaper prices.
Or, you can keep saving, and buy a really high mileage (60-90K) 97 Boxster for around $25K (maybe even better, you never know). As much fun as P-cars are, they're even better in convertible form! And mid-engined handling is hard to beat
