Many years ago, before retiring, I was a realtor. I actually adored my job, however the last place I sold was the final blow. When I did my initial walk-through before putting the home up for sale, I was shocked. There was a trail that led from the study den door to a chair, then on into the dining rooms. The couch was piled high with trash plus there was such a stench that I about made me gag. I asked if the cooling system still worked, plus when was the previous time they had changed the air filter. The person looked at me carefully as though I were crazy. She asked me what I suggested by air filter. I explained to her that I was planned to hire a HVAC supplier to come to the home plus inspect the HVAC system, So, in the meantime, she needed to get the home cleared. She was moving into her daughter’s in the next week so she didn’t have time to clean. I knew this was going to be costly, but I hired guys to come in to clean the house, plus only reclaim some of the furniture if it was reclaimable. A week past and the home was cleaned out, plus I was in the home with the HVAC tech. He said the HVAC was only about 5 or so years old, however it was shot. The air filters had never been hosed, plus there was dirt all in the inside. There were cracks in the air ducts plus he actually thought it would be cheaper to just put in a new heating & cooling system.