Warning the Buyer
Answer: In Pirkei Avot we are advised to avoid bad neighbors. This is extremely practical counsel because the wrong kind of neighbors can be not only spiritually detrimental but can also make life unpleasant.
One of the commentaries calls attention to the fact that the term used in this advice is harchek rather than titrachek. The latter term would have meant "distance yourself" while the former suggests that you have an obligation to keep others away from such a pitfall.
You must spell out to the buyer the problems you have encountered which may seem to him to be soluble or tolerable. It is then up to him to decide whether he wants to go through with the deal.