Cleaning mold is not as simple as scrubbing with bleach.  Bleach does not penetrate most surfaces, so while the top of the mold is gone, the roots remain.  You will need a product that is EPA registered to kill mold and destroy the roots as well.  But, there are more considerations...

First, mold cannot grow without moisture.  So, to fully resolve the mold problem, a professional always wants to know WHY THERE IS MOLD, not just treat the mold problem.  This can be an easy assessment, like a recently flood or water leak; or something hard to figure out.  That is where years of experience is important.  We've literally seen it all, and likely have a fair idea of where the true problem originates.

Secondly, the size of the problem is a concern.  Anything that is less that a square foot is probably something easily fixed.  At ten square feet, the concern level raises as this may be a growing issue.  At, one hundred square feet, (10' by 10'), we consider this a potential biohazard.  At each level, we must step up the process of diagnosis and treatment.

Third, mold is constantly send out spores, which are the seeds of the mold.  These are microscopic and easily spread throughout the house via your ac/heating system.  Mold spores can be allergenic or pathogenic.  While much of the population may ignore mold or mold spores, there is a sizable number who are adversely affected by mold and mold spores.  So, more than cleaning up the mold, it is incredibly important to clean-up the general area ... and the whole house after the mold is cleaned up.

This is why calling in a true mold professional is important.  Half measures are only stop-gap efforts that allow the mold problem to come back time and again.  Plainfield Mold Inspections is part of the MoldAdvisors network.  They are professional, honest, and OSHA trained for mold inspections for residential and commercial buildings.