For a cheap alternative, I got a dog's cage. The wire spacing was too big, but I've covered it with mesh.
Here's a picture just to give you an idea of the size (Yes, that's THREE people in there):
And here it is when it was first set up:
It was home to just my two girls, but it's soon to be home to four boys. I should tell you that these pictures are from when we first got it-since then it's changed a lot. There are no wooden platforms, and all wire-platforms are covered up. And there are a LOT more toys. Hope you like it.

Might be an idea for a cheap cage if anyone's looking? I got this of ebay for £18. Second hand, yes, but in good condition as dog's aren't kept in cages very much. Hehe.
I love the other cages on here by the way.

Given me some more ideas for toys..
xx
Sophie and the boys; Fergus, Oscar, Rufus and Zebedee.