Yep, what they said ^^^
One thing to keep in mind with co-ops, though, is that they usually involve a lot of waiting (not always, but usually). Getting people together and getting the initial order placed usually goes pretty quick, but then everybody has to sit back and wait until the manufacturer/vendor ships the order, then wait for the co-op organizer to pack and ship everybody's individual orders to them.
They're a
great way to get things really cheap, but are generally not a good option if you want your new toys right away. Patience is necessary ;-)
I just wanted to point out the time factor because I've seen a lot of people new to co-ops who get upset when things are taking too long for their liking. It's always best to know what you're getting into right from the get-go and I hope that info is helpful to you