I understand. I've had a few "omg, these 'free' eggs are going to be really expensive!" moments but building the coop and raising the chicks has been a great experience. It's a great hobby to share with my husband, plus I've learned how to use some power tools. It's been so fun.
I hope he comes around, and ditto others on looking for scrap wood on Craig's List. Our recycling center gave us some great 2 x 4s today for free. Swing by one and check it out. Good luck!