I started out with a freebie Craigslist doghouse, inside of a $125 Craigslist 12' x 7' chainlink dog kennel, for 3 hens. I modified the doghouse to add two nest boxes on the back, and a better roof, that could lift off for cleaning.
To make the the chainlink kennel more predator-resistant, I surrounded it with 4' hardware cloth, bent at 90 degrees so that it went 30 " up the sides and 18" out from the sides along the ground on the outside. I put cinder blocks all around the outside to hold down the layer of hardware cloth that was sitting on the ground. Above the hardware cloth that went up the sides, I attached chicken wire around the sides and over the top.
Sorry this picture looks so junky. We'd already started building a bigger chicken yard attached to it, but you can see the basic modified dog house and modified kennel.
Chicken Math happened - we adopted a rooster, then our neighbors moved and left us their chickens.
This is looking at the same chainlink kennel from the opposite side. Using 10-gauge wire, we attached a 4"x6" along the top left wall, a 4"x4" along the middle, and a 2"x4" along the right side. This created a sloping surface, where we attached the green PVC roofing.
You can see where we were starting to build the new. bigger yard, by installing 4"x4" posts and white boards between each post, attached by metal framer brackets. You can also see the new gate, "Dutch door" style, made out of freebie pallets with hardware cloth attached.
Our neighbors who moved away and asked us to adopt their chickens had this awesome waterer made out of PVC and 4 chicken nipples spaced along the bottom pipe. You can also see how the new yard is constructed, with poultry wire surrounding all sides, plus 4' hardware cloth going up from the ground 30" and extending out along the ground from the bottom 18*. Then welded wire going up the sides from where the hardware cloth ends, to the boards attached along the top.
On the left third near the top of this picture, you can see the edge of the green PVC roof where it empties into a black gutter, to direct rainwater into the red and white barrel. The posts in the middle of the yard hold up white PVC trusses, which support poultry wire covering the whole yard, to keep them safe from hawks and owls.In the foreground, you can see how we attached the lower hardware cloth and upper welded wire on the outside of the poultry wire, using screws and washers.
The footing in the run is a thick layer of free wood chips, courtesy of Chip Drop, plus various logs and branches I salvaged from downed trees nearby our property.
All told, this whole setup which is now suitable for about 40 chickens, cost us between $1000-1500. The most expensive items were the 100' of 4' hardware cloth, other rolls of wire, and the various deck screws, washers, and gate hinges and hardware.