I have a building that originally was for pigeons and converted to chickens. It is 8 ft wide, 12 ft long and 8 ft high. The back wall was covered in pigeon nests that was why it was this high. It has been moved once already. I built 4 and 3 have been moved in the past you just have to have the proper trailer.
These cost me about $400 in materials plus much labor. I'll also throw in a feed box that will hold 200+ pounds of layer and they can eat for months without you having to do anything. For another $30.00 I'll throw in an automatic waterer that you never have to fill just wash out every so often.
The lumber etc lying on the ground was a additions I disassembled.