The basic premise of a bike co-op is to provide a workspace for people to learn more about maintaining their bicycles. At the Bike Project, you can fix up your own bike under the guidance of volunteers, buy a bike-- typically for under $200--or build a bike from their used parts for as low as $25.
The volunteers are generally knowledgeable and helpful. If you willing to take the time to learn, you can get your ride up and running on the cheap.