The February Growing For Market has a low cost germination chamber in it. He basically uses rigid foam insulation to make a box and has an aquarium heater hooked up to a thermostat. I've got one that uses a steam pan heater, like caterers use, that plugs into an Inkbird thermostat. All that sits inside a non functioning freezer I got super cheap on craigslist. I bet a used crockpot could work just as well as the steam pan heater in a smaller chamber.