Fixing mold problems is usually extremely expensive. In the current market in Iowa, I'm going to guess that if you have a 50,000 offer you are probably better off accepting the offer and moving on. I have recently relocated several couples to & from Waterloo & it appears that our markets have suffered similarly... In Des Moines we are off 50% year to date & we have learned that we probably would take at LEAST a 15,000 hit on a property with mold or similar issues. The information on remediation would be good to have, but if you risk loosing the buyer I don't think I'd take the time... The ultimate solution to mold is to completely remove everything potentially damaged, fix the actual problem (wherever the moisture is coming from) & then replace the interior fixtures... Drywall etc. It's expensive. And, even if you do the work, there's a stigma that's associated with properties that have had mold & you still are obligated to disclose that it has exisisted in the state of Iowa.
Good luck, and don't hesitate to ask if I can assist you further!