electric fan kit

ok so i looked at buying an electric fan kit and i wanna make it so it plugs into the thermostate housing and turns on when the engine needs it so it dosent just sit there and run the intire time. but what im wondering is there a free hole in the houseing im not afraid to make one if there isent i just dont want to if there is allready one there. if you have done this to your car please send me a pic and info on how you did it. i know my way around a toyota well my dad does his a certified toyota tech. thanks