Because you are purchasing a short sale, you are more than likely buying the home "as is." The owner probably does not have the financial ability to remedy the problem. The seller's lender, who also has a vested interest in the property could be asked to cure the mold issue because it is unlikely that your lender (if you are borrowing to purchase this property) will lend to you under the circumstances. It has been my experience with other short sales, that the seller's lender will probably not remedy the problem, and they may even threaten to not refund your earnest money because the home was being sold "as is." On the other hand, a Wisconsin contract states that the home is to remain in the condition it was at the time you agreed to purchase the home. I assume mold was not an issue at the time your offer was accepted. If you believe the problem is serious enough that you do not want to have to cure the issue once you were to take possession, and none of the other parties are willing to on your behalf, then I would attempt to cancel the contact and get my earnest money back. This may require an attorney's representation if the seller and their lender is uncooperative. You would think that cooperation and getting the home sold would be in the seller's and their lender's best interests, but unfortunately it doesn't always work that way.