I don't know what CA's rules are but around here for insurance purpouses you have to have one if working one someone elses property for profit. If the guy said there was a problem, then said he was fine then came back with I don't have one, I'd tell him to get lost and find someone else..
House Information: Build 1996, 1500 sq ft basement, 1500 sq ft 1st floor, 800 sq ft 2nd floor, 560 sq ft unfinished attic space on 2nd floor. Insulation: Attic blown fiberglass, walls R-19, Basement R-19. HVAC: Trane xc95m fully modulating furnace, single zone, Trane XL20i commiunicating AC unit, TCONT900 Communicating thermostat.