Look into wood chips from a tree service or the city dump (where the tree service dumps their mulched wood). My sister used the site below and had them within the same day. Minimum/no cost.
https://getchipdrop.com/
Also PLEASE give your chickens a minimum of 15 square feet per chicken outside if you possibly can, especially if you want to keep a rooster. You will avoid so many bad behaviors starting that way. Once some of them start, they're nearly impossible to get rid of, and your chickens will be miserable. Miserable chickens lay smaller eggs. No joke, I relocated two of my lowest hens to my new coop and all of a sudden those two plus many of the remaining lower pecking order hens in the original coop started laying larger eggs. They were so much less stressed!