To cover the lid, as you can see, I cut out a square. I went to a hardware place and got some wire mesh.. which is very cheap by the way, and I taped it on with a heavy duty tape. A lot of people use washers or screws or whatever, but tape was easiest for me. On the entire cage, you'll probably spend about $20 for the cage, and supplies. Here is a link with great information on bins as cages:

Bins as Cages