We have a pole barn that was here when we bought the property. We did not build it. I would not attempt to make a homemade pole barn. BUT if I choose to, I can walk into every coop or pen I have for the chickens and goats. And of course the barn is has more than enough room to walk in.
Here is a method i recommend for a beginning coop. Find a used shed, add nests and bars if you feel so inclined, make the shed sectioned off for people and chickens. Venting is typically needed to or the door will need to be left open.
Here is a link to a used shed in Indiana that costs much less than a coop of similar size.
http://indianapolis.craigslist.org/grq/4903280608.html
I may check out some local lists like CL and Freecycle and see if there is anything I can use to maybe add on to what I have....even if my son helps it might save him some work.
That looks like a nice building in that add.