In many counties, a pole barn requires no permit. By code, they are generally intended for storage of animals or diesel-fueled agricultural implements, etc. Having said that, many people build them, pour a floor, and they become a shop. By typical definition, a pole barn does not have a foundation, but rather uses 4x4 or 6x6 poles buried 4-6' underground, spaced every 8'-12' or so, and then have supports and siding attached to them. There are dozens of pole barn building companies all over Colorado who could help answer your questions.
Colo Springs, CO
'78 FJ40, '89 FJ62, '98 4Runner