It's a fridge, so it's enormous (though I guess people could use those half sized bar fridges, but that's a lot of work for a small space)
Whenever you re-use trash you get more than you could afford, you use things stronger than you could ever afford, a larger quantity than you could ever afford, already built a lot of the time, so it's too great to not look into.
The fridge fits as many chicks as I have at a time, average fridge, 50, or a one piece big stand up freezer on it's back, probably more than 100 without a sweat.
I keep them outside when they annoy me inside. The current batch I keep in a tall cardboard box with a towel in it, they are dead quiet at sleep time, noisy when I feed and water them, each day I put them into a big crate I got free from some factory, it's bigger than a washing machine and I put a grill I found over it. It houses some other chicks that are now free ranging in the day, so the chicks sometimes spent the day in that just to be outside. I guess I will put them in the freezer later because they are not ticking me off at the moment, it's summer here and the crate is in the shade. There are more in the incubator, but at the moment I am putting them in other places for other reasons.
In winter, they can't be just put into a crate for the day I guess, so that is when the fridge comes into it's own because I put them in there, they can use the little yard to go outside, the yard is made mainly from supermarket shelves and fridge shelves. Occasionally I did put a heater in the fridge, but I would expect in the future when I hatch more than 6 at a time a towel inside the fridge without a heater will probably be enough down to freezing. More than 6 then for sure, I don't expect it will need a heater. The need for a heater is judged by if they chirp rather than sleep quietly.