Not cheap ($500), but materials alone for this cute playhouse would cost WELL over that price. It's a 6x8 w/lots of windows and front porch (extra footage....could be screened/wired in). I just told DH that if we didn't already have a coop, I'd be buying this...
http://louisville.craigslist.org/grd/2013798845.html

http://louisville.craigslist.org/grd/2013798845.html