I used about ten large sheets of graph paper to plan it out. Just a number 2 pencil, a good eraser and a clear plastic drawing scale is all it took. Pretty easy cheese, and I was amazed at how inexpensive this project was, compared to some of the prefab coops that are out there on the market. Backyard chickens dot com has all of the design criteria you could ever ask for, and there are a million different ways of building a coop, and most of them are pretty good.
We also took 2 months to build our coop, and spread the cost out so we could pay cash for all of our materials. No charge cards, no loans and no interest! I also purged my shop and garage for as many materials as I could find to re-use, paint in particular, and that saved a ton of money too.
The other motivation quite frankly is preparedness. If all else fails, we have hens and hen fruit as long as we can feed them, and we have that taken care of as well. In a barter economy, eggs are a valuable commodity....