Good afternoon! It sounds like you had quite the experience selling your house in Southern California last year. You were in a hurry to sell the house, so you negotiated the price down with the buyer to make it more appealing. After the sale, you moved to another location and thought everything was over and done with. But one year later, you got a bill from the contractor that the buyer hired, claiming that there was mold growing behind the wall and that you are responsible for repairing and abating it.
If the mold wasn’t indicated during the home inspection period, then you don’t have to entertain the buyer’s request for $5,000. You don’t have any responsibility to the buyer after the sale has been finalized. It was the buyer’s decision to purchase the home, and they should have discussed any potential issues they were aware of then. If they didn’t see the mold, then they bought the home with that issue and they would have to prove that you knowingly concealed that information from them.
If you’d like to get more clarity on the situation, you can ask the buyer to provide the home inspection report, as this may have noted the mold issue. In any case, you don’t have to entertain the buyer’s request for $5,000 as it was their responsibility to purchase the home as-is.