Wanna do it on the cheap? Check your local pharmacy and pet shop for free styrofoam coolers. Add, some light sockets from discarded lamps, a piece of glass from an old picture frame, a computer fan wired to a 12V telephone charger plug, and a digital thermostat. Do a google search for Rush Lane Poultry for the many "how to build an incubator and wire a thermostat" videos he's made.
Add a few tools including: drill, screw driver, razor knife.
Add some red neck/MacGuyver doo-dads: duct tape, electrical tape, wire connectors, bits and pieces of this and that, 1/4" hardware cloth, heavy duty tin foil, nuts/bolts, fender washers, silicone caulking.
When it's all done, put sealed water bottles in to approximate the weight of a full set of eggs, get it running, and check your temp variation in all areas of the bator. Add extra venting or tin foil baffles to redirect your air flow. Check and re-check it till you get it right.
Finally, CALIBRATE, CALIBRATE, CALIBRATE!!! A thermometer is lying to you if it has not been CALIBRATED!