I love the idea of taking old discarded things and turning them into something useful again. Basically I come from a long line of rusty nail saving, do-it-your self rancher types, and I can't stand to throw anything away. So I'm trying to think of different already manufactured structures that could be repurposed as a travel trailer. This is mostly a creative exercise, I'm not sure that I will actually do this.
Here are a couple things that I thought of off the top of my head:
The abandoned shell of a VW beetle
A garden shed
A 600 gallon water tank
A section of light aircraft fuselage
Does anyone have any other ideas?