UNfortunately, the animals are cheap$ but it's all of the other stuff that we buy to Keep them/Use them to breaks our wallet!
Like the comets I bought last year, cost less than 30 cents each. 15 survived in the 100 gallon water tank I was using during the drought for one of my cherry trees and I wasn't growing mosquitoes there.
Couldn't stand to kill them, so I spent nearly 50 bucks on a 10 gallon tank and extras to keep them alive until May.

When I get chickens again, I will use my "Peck and Play," in my garden. Since the big garden is visible from my firepit I will sit and burn and keep an eye on them and only keep them in it when I can babysit.
MY GS would probably only chase them. Once in awhile a neighbor's dog gets loose, boy chasing him, and, being a Pitbull I am sure he would like to have fresh chicken.
I can keep my pellet gun AND a shovel close by if I am outside and the dog shows up again. A strong whack to the rear end would discourage him.
If you want your chickens to work them in your garden AND walk away, maybe even leave them out overnight, it WILL cost you to buy, or time AND money to build something that works.