As far as getting your structure on the cheap, what are you needing to end up with? It might be possible to take it in stages. That won't guarantee the cheapest building in the end, but allows use of the building (once erected) in between stages. It allows you to save up piece at a time if you want to do it without loans, too. Also, in your area can you dig a hole 3 foot deep without blasting through 2 feet of rock? You might exhibit the mad picking skills you have honed on used machinery and obtain the free, steel free span building of your dreams, but if not, there is going to be a lot more laying around in the way of free/cheap used pole barn tin. A caution on "recycled lumber", it is often costlier than new to tear it down, pluck the nails, and cut it into something usable. Dismantling a pole barn would be more doable than residential type framing if you had to tear it down to get the tin anyway. A further caution on the rainbow building, you will never paint it and it will be ugly as all hell. Mine is). I look forward to hearing what the end result needs to be. I can help devise a strategy to get there.