You have found a great house and the listing photos look like they're from a magazine. You schedule a showing with your Realtor and <BAM> the smell of the house hits you like a boxing glove. It happens. It even happens in really clean houses. It doesn't matter what the cause of the smell is, it's likely to be a deal-breaker. The worst part is that if you've lived in the house you probably can't smell what the buyer is smelling. Ask your Realtor to give you an honest app