I think you take Grant's advice with a grain of salt. 

In 6 months they broke 3 light fixtures - I had reports their kids were spraying a garden hose from the outside of the house into the kitchen, broke a large kitchen cabinet door, broke several plastic pieces of a new higher end Fridge, fist sized hole in the wall, carpet stains and the entire house may need another repaint, damaged woodwork, scratched kitchen cabinets, stole the curtain rods, curtains my wife spent a lot of time picking out stolen, destroyed the back yard - let the weeds grow several feet tall in the flower beds etc.  

My AC evaporator luckily has an access panel that is easily removed and then a service plug in the side panel of the coil (plastic disc wedged into sheet metal) that I was able to remove, liberally spray down the coil on the 'incoming air side' with cleaner bought from lowes, and carefully spray some water onto the coils from the easily accessible 'outgoing air' side to back rinse after waiting the recommended time. 

I've seen the spray-in foam insulation for walls, but I am not sure if it would work in a ceiling or if that's advisable.

This is all pure speculation, though, so such comments should be taken with a huge grain of salt; don't build a business model with this as the foundation.

All of this advice should be taken with a grain of salt as I am not a tax adviser.  

Each year I will do my best to keep the salt from the snowy roads from rusting the vehicles.

It's like in the show "Breaking Bad" where they have a pallet of money in a storage unit and the wife goes in to spray so the bugs don't eat it all.

Call Terminix and have them come spray the house for like $130 or so.

I'm new enough to investing where you'll have to take my opinion with a grain of salt.