I am in the process of building my coops right now as well, and have been collecting free or nearly free materials from craigslist and friends and family. I am using a shipping crate, very old oak wood flooring a family member was taking out of their house, and a few choice pieces of lumber from the hardware store. My coop, here in Ohio, will be a 14' x 14' coop with a divider in the middle, wood tongue and groove flooring, double hung windows, and tin roof. The whole project is going to cost me about $250.00 with the majority of expense being the 4 x 4 posts for getting it off the ground, and the chicken wire to fence it and the run in. Also, I have made a separate basic tractor for meat chickens that I will only use in the summer. I plan to run electric to the coop for lighting and a heat lamp just in case we have any really cold nights in the winter. The light we will be using was reclaimed from my fiance's work.
Although I am now known as the crazy chicken lady to all of my friends and family it has really paid off! Remember, it never hurts to ask if anyone has any old materials laying around!
Good luck to you and your chicken adventure!