Here's my coop I just finished. It's 4X10 with the coop being 4X4. Overall cost about $300(less if you have some scraps around). I didn't have any detailed plans. Just looked at some pics on Backyardchickens.com and started building. I used 2x4 lumber for the frame and 3/4 sheeting. I had some scrap fence boards I used for the roof and just stuck some roll roofing on top. I did stain it with a water-proof stain to try to get longer life out of it...especially since the sheeting was not meant for outdoor use without some kind of wood preserver. It's pretty heavy being 2x4 framing (probably 300 lbs), but if you wanted to put skids or wheels on it you could easily move it around the yard with two people or even better a riding mower and a piece of rope.
As far as materials go...2- 10ft 2X4's for the bottom sides, and about 20 8ft 2x4's for the rest. 2 sheets 4x8 plywood (3 if you need it for the roof too). A bunch of screws, etc and a 50 ft roll of 36in poultry fencing. If you want a good video of where I got started search youtube for "Harriet's House" It helped me figure out everything except I did my roof totally different and in my opinion much easier. Remember...it's just a chicken coop! And if you build your own you will get much more satisfaction that from ordering a pre-built one for $500 or more. Good luck building your own and if you pour your sweat and love into it your chicken will surely love it too.