Seems like people like to build their own cleaning machines, but I have not seen any mention of building a hot box.
Not to much experience needed for it, just a burner assembly, a coil source and the correct placement of a few switches, and some basic wiring. I am not sure what a coil and a wrap would cost, but seems like a fun prodject for the dollar savers.
Grainger Industrial Supply: Burner,Oil 4NU98