This is what you can do with cardboard (without any glue) and with lots of time
I made it in preperation of my two little Roborovskiis which I'm getting (very) soon
The top floor is open ended so I can put it next to a shelf and they can slide/go down the toilet tube. For a second attempt at cardboard hamster houses, I'm quite pleased with it, but any suggestions for the next one would be great
And here it is, sat in my Rody hamster cage to give a sense of scale --