Word.


Buy this bike from walmart for $149.00. It's a single speed so you will need to convert it to fixed gear.
Mongoose Cachet $149.00


To convert it to fixed gear, buy this wheelset. Eighthinch Amelia's are cheap ($119.50 shipped) but will be strong enough to outlast a mongoose bike. The best part is they come with tubes, tires, a 16T fixed cog, a lock ring, and track nuts. They're pretty much ready to go out of the box.

Eighthinch Amelia $119.50


This leaves you with $31.50 which should be just enough to pay your LBS to do all the work for you.

This combo is probably the cheapest way to get a non-blemished, brand new, ready to ride, fixed gear bike if all you have is $300 and you don't know how to put a bike together.