I built this A-Frame Chicken Coop using the Ana White plans. It turned out adorable, strong, and I am very pleased. Final cost was $250, and it took me 4 days (in real time, as a mom of 3). One Saturday at Lowes shopping, one Sunday afternoon cutting, and two days of assembly. Then a 5th for painting. Give or take a dozen extra runs to the hardware store! My brother-in-law helped cut the angles on his miter saw, and my uncle helped with assembly. I kinda doubt this could be done for $100 - maybe if you have a bunch of scrap materials and spare paint. We even have 7 or 8 hens in there! I only intended 3 to live in it, but my uncle added the extras and they all get along happily. I found the roof cap at Home Depot (didn't find at Lowes).
I would also like to point out that I was very afraid to do carpentry - I was afraid to even buy the lumber. But I asked for a lot of help from a lot of Lowe's and Home Depot people, and resisted the naysayers, and just got brave and did it. And it came out beautifully! If you are new to using power tools, get someone to assist, and you would need help anyway with holding things up while another drills.