You can do what I did, which is use 1/4" welded wire (hardware cloth) to nearly completely enclose both run & coop. I was lucky enough to get a 100' x 4' roll of hardware cloth on craigslist for $80. The run (attached to the coop) is framed with CCA 4 x 4's and covered with hardware cloth (wire is attached with scews and fender washers). Since I had a very limited space to build, half of the run sits on a concrete sidewalk, with the other half being a dirt strip that abuts the concrete driveway and privacy fence. I dug down along the driveway and base of privacy fence and buried the hardware cloth about 4"deep against the concrete, nailed it to the concrete with masonry nails, then filled the trench with concrete mix. The coop is within the run and attached to a shed, with the coop being elevated about 18" off the ground. Both shep and coop have a corrugated metal roof. When building the buildings, I attached 2' of welded wire to the base of the walls all the way around, then put the siding on top of the wire. I was also lucky enough to scrounge some Hardiboard, which is concrete siding. Not even a porcupine can chew thru Hardiboard. I still need to put hardware cloth over the outide of the windows and over the ends of the eaves. Think along the lines of using as much welded wire (hardware cloth) and Hardiboard (and/or Hardibacker if you don't care much what it looks like) and metal as you can to cover the outsides and you'll be good. Just keep checking craigslist and freecycle, you'll be amazed how much you can scrounge. I think I spent about $300 to get a shed, coop and run that should've cost over $2,500.
