We are in the middle of a "cheap" build, too. I'm the architecht, hubby is the engineer/contractor, and the kids are the decorators in charge of paint. Here are some things we've done to cut costs:
1. We've made several trips to the Habitat for Humanity Restore Store. Basically a builder's Goodwill. They have oodles (don't get to use that word enough!) of doors, windows, hinges, knobs, and even a selection of used kitchen sinks if you want them. I have a stack of really nice vents, knobs, and hinges from them, but my real find was the paint. I got a 5 gallon bucket of Sherwin Williams' top of the line exterior paint in a color that's not ugly for $20. Even oops paint at Home Depot would run about $100! They are a great cause and a great resource. Google "Restore Store" to see if you have one nearby.
2. We're using 2 sides of an existing fence for part of our run.
3. A friend finally talked her husband into cleaning out the shed, and we hauled away a bunch of lumber...even some nice 4x4's and a door with a built-in window, which we've cut down to be our henhouse door. Let people at work know what you're doing, and you can help them out by hauling away stuff they want to get rid of , and you can help yourself out by getting free materials.
4. Shop around. Our 1/2 inch mesh was our priciest outlay, and we didn't want to go cheap on protection from predators, as we are overrun with carnivorous critters at our place, but we saved a modest chunk by checking all the local sources.
5. Lumber stores sell their slightly damaged lumber at a huge discount. I figure the chickens don't care about knotholes or rough edges, and paint covers up a lot of ugly.
6. Instead of real windows, we're making prop-open hatces with mesh over the opening. In hot weather we can open them up to cool things down, and in cold weather we can bolt them shut. Even with cheap windows from Restore, I had no idea how to install them, so we decided to skip it.
You understand our coop is only half-finished, so I can't say for sure we know what we're doing as far as building, but I am a master at penny-pinching. I hope these scavenging ideas help.
Happy building!
--Nikki