If the REO (real estate owned) parcel is not occupied, the bank that foreclosed on the property has no legal duty to remediate any known mold issues with the parcel unless there is an order issued from a court mandating some form of remediation or there is some citation issued by the local health department or building and permit department as to the property.If you are interested in the property that has some apparent mold issues, you can preface the offer that you may make for its purchase on the estimated cost to remediate if you acquire the property with its known condition.