Buy a used bike.
Remember that you'll need $150-200 in additional stuff when you get the bike, like helmet, shorts, shoes, mini tool kit, gloves, spare tube, etc.
__________________
Spectrum Ti Super | Landshark Roadshark | Serotta Colorado | Gunnar Crosshairs | Trek 9800 | Santana fillet brazed tandem | K2 Easy Roller | Dawes (BD) Bullseye 1x1