carport with straw bale infill?

I've been pondering building a small super inexpensive yet insulated and livable structure. My budget is about $3000. First I was thinking about a pole building with straw bale and gravel bag foundation. Just a basic 200 sq ft or so living area that could be heated with a rocket stove.

Today I was driving down the road and saw a metal carport and thought to myself hey that could work instead of all of that lumber! since carport kits come with supports for the roof and walls. Also it would take about a day to set up. Anyone think this would work alright? my main concern is condensation getting on the straw bale and rotting them. Also how would one vent and insulate the roof? These carports are about $1000. Which would leave me roughly 2000 for starawbales and finish out.

Hey Dave. Nebraska style! Skip the lumber in the walls and bear the roof load with the bales. Carports are cool but they shelter cars nicely.

Thanks Tim I am indeed going to go "Nebraska style" with my building! I found some trusses and free metal roofing so the carport idea is out. I'm excited to get started I will post pick of my progress as I go along.