Keep it. As a co-op bike it isn't worth that much because everything there is probably used and old except for maybe the rear wheel (hard to find fixed wheel at the co-ops) and bar tape. Not to say it's a bad bike, but it will be hard get another bike that seems good for $50 and I don't think you can even make a bike at the co-ops for $50 unless they understand you have little money. What are you going to use for transportation without the bike?