The barn was designed out of foamboard, and set on some mdf board to easily carry it around. The simplicity of the design was straightforward and cheap. It probably only cost me around 5-6 dollars to put the barn together overall.
Foam board, 2 dollars (of which I didn't use the whole sheet), mdf board (small amount of a large chunk from the store that was still in the attic), 50 cent pieces of wood that were bought at Michaels, 50 cent paint that can be found on clearance all the time next to the painting section at Lowes (good tidbit to know).
The only details in the foamboard were introduced with a ruler and a modeling knife (thickened with running a pen through it when done).