I had always heard black mold was toxic. I looked it up on some government health websites and actually they have no clear evidence linking black mold to any health issues. They just warn that it could pose an affect to people who may already have respiratory issues. They just said be cautious. I do not know much about it just from what I read. It might be bad and it might not, but I do not really want to chance my family's health. Also if I want to sell it would be hard if not impossible to do with signs of mold. Thanks for everyone's advice. Lowell I will probably do the cement board, bigger vent, and tile.