Made my brooder today! Mom got a very large, free cardboard box...but it had no bottom, so we cut it down to size(it's about 1.5 feet tall inside now) and stretched it around a wood pallet. Used the leftover cardboard to line the top of the pallet(to support the weight of the sand that I'm using in the brooder). We doubled up a large, heavy-duty plastic liner and stapled it to the sides(plus put tape all the way along the top edge of the plastic, not only to hold it in place but also to prevent a chicken from somehow getting behind it). Put in the sand...Used 2 pieces of chicken wire from a roll of it that we already had laying around as a top. Though only 1/2 of it is on in this picture...Total cost, not including sand... $4
Sorry, don't mind the bare mattress...sheets are in the washer!