httpv://www.youtube.com/watch?v=oSqlQ-P5CZQ
Here’s a good video showing how to build a super-pro looking dual chamber compost bin. I’m guessing this would cost between $40 and $50 to make, but it sure looks nice! He doesn’t specify the size, but I’d recommend 4′ x 4′ x 4′.
If you want to do this for free, find a few pallets and tie them together with coat hangers. Not as nice looking, but you’ll get the same results though.