When my interest first started with snakes a year ago, I wanted to use glass tanks (aquariums), because I'm an aquarium guy and just had them lying around unused. But as I was doing my research, and getting ready to get my first snake, I learned more about the PVC enclosures that are readily available out there.
I got my 4x2x1 from Animal Plastics, and I think for the most part it was fairly cheap (considering what some of these enclosures cost). And, the locks, lights, shelves, etc, are all optional... and if you have any other ideas it seems that Animal Plastics is fairly flexible for some customizations.
Just a thought.