At the first start up of the day do you see "white smoke" coming from the tailpipe? (Leaking head gasket).
Do you have an "oily film" on the inside of the windshield and/or wet carpet under the dash? (Leaking heater core).
No? Good. Breathe a sigh of relief.
Get a mirror and strong flashlight and look around under the hood. Check the water pump, hoses, radiator, etc.