Jim, you can do it as cheaply as you want, almost. This is the type of coal forge I started with. I used an empty freon jug from an air conditioning place, cut it in half, put a pipe in it, drill holes in it. Then after that, I put in some clay I dug up from a river bank. Add a hose and a hair dryer along with charcoal, it got hot enough to burn and melt steal.
https://goo.gl/images/bvf7am