The most common method to hide mold is by simply painting over it which also happens to be the absolute worst method.
Unfortunately, this is exactly what most property managers, landlords and or homeowners do when they have mold on walls, ceilings, wood and or drywall.
Many do it ignorantly and some do it purely for profit because it's the cheapest and fastest way to hide mold.
Don't be this person... Call SERVPRO