For the majority of surfaces in your home, bleach won't actually get rid of your mold problem. It's the "iceberg effect." Visible mold is usually a small percentage of the actual amount of mold growth. Bleach can't kill mold on porous surfaces like wood, and while tile or fiberglass surfaces can be cleaned with bleach, often the mold has spread far deeper. The reason why mold remediation companies don't recommend DIY cleanup isn't that they want to make more money; they know, in their experience, that a mold problem is usually far more invasive than can be seen with the naked eye. Simply cleaning the surfaces can provide false assurances that you got rid of the mold, only to have it come back time and time again.