Sounds like he should be good at this.I believe most people just turn them on. Some,of course,have service contracts for maintenance.The evaperator,the inside unit,needs cleaning depending on home usage.Smoker,no filter,or anything that put a strain on the unit. Have a contractor do this. On the condenser,the outside unit, as mentioned before, keep clean. Always spray from the inside of the unit out. You want to force the dirt out,not into the unit. Easy to do. TURN POWER OFF. Check twice. Remove fan cover and move out of the way without removing any wires. If your not sure about this,have someone else do it. Hope this helps, Ron J. P.S. I think the biggest problem with the outside is grass being sucked up on the coils while cutting grass.