Sounds awesome! That's exactly what I'm planning to do!

People have done it, and surprisingly it is actually cheap. We just dry some dirt and you can mix with sand for hamsters, gerbils or mice. You can also use dried grass or dried leaves. Natural branches, some simple rock caves and bark hiding places. The only thing to avoid is a high level of moisture, since this isn't healthy for rodents.

Best of luck with your plans!