Pallets is a good idea! I'm trying to find something already assembled... the run is going to be a lot of work, I want an easy coop, LIL!
Here's a nice wood one?
http://www.samsclub.com/sams/natural-pitched-roof-dog-house-medium/prod1350372.ip
I have this one. I bought it for my very first chickens. I added a 2-in dowel inside for them to perch on. I also set it up on a frame so it would be off the ground and offer an area for them to find shade under. I put a cupboard door on it. I also put in a small block on the two front corners where the lid comes down so they've have ventilation.
After a year, I now use it for a grow out/broody coop only. I have nothing in it year round. You really would only have enough room for 2 standard/3bantam birds. Its just under 10 sq feet inside. The hinges are also weak. It is nice to open and clean out though. I have replaced the hinges with a better after market set. ALSO, cleaning is a breeze since the floor is remove able in 3 sections. SO, if you have a predator proof run, that is roofed as well, you could take out the center floor section, and build a ramp down from that and the birds would be able to go in and out at will. There is NO ROOM for a nest box however... That is why I only use it for growing out.
For this 100 you are going to spend on it, you can spend that same amount, and build a box that is 4x4x4. You'd need 3 sheets of ply, 10-2x4s, screws, and hinges... It's a simple box. Only you'd have one piece of the ply cut at 3 feet and 5 feet sections. The other too pieces of ply cut in 4 feet sections. You will then have to angle cut two of the 4x4 sections so that one side is 4 feet and the other side is 3 feet. This will give you your slanted roof. You could even hinge it if you wanted. Add some ventilation, heat vents are great for this. Oh, and cut in a door on the front that is large enough for you to be able to clean out. All in all, you'd spend 100 bucks, do it yourself, have a stronger and more durable coop. You could find some of the things you'd need at a habitat for humanity resource store... Use an 18 gallon tote flipped over, with a hole in the side for the girls to use as a nest box, or two, one on top of the other, or side by side. Then, you could have 4-6 birds comfy enough even if they had to stay inside because of snow..
You will not be happy with the dog house as a full time coop. You really won't. Its OK for chicks and mama hens to raise some chicks, but not for laying hens. It also works nice for meat birds to sleep in at night... I have used it for that too.