Water damage is one of the ways that mold can grow in a home. Wherever there is water, mold is likely to grow. If you find any sort of moisture in your walls or on your floor, you should repair it immediately. You need to find the source and fix it.
The bathroom is one of the many rooms that mold cna grow in. Since the bathroom is so oriented with water, the pipes will eventually wear down and may need to be replaced. Occasional maintenance will help the pipes stay in working shape, but accidents do happen. There may be a leak from a loosened screw or some may splash where you can’t see it.
There are a few ways to fix these things at http://www.damagecontrol-911.com/black-mold-in-your-bathroom/
If you find mold in your bathroom, then there are a few options for you. You should never leave mold unchecked. It can grow out of control and spread to other surfaces from your bathroom. You can call a mold remediation specialist that will get rid of the mold for you.
However, that may take a lot of time and money that you don’t have. If you are skilled with carpentry or sheetrock replacement, though, you can certainly solve it yourself. It’s only a matter of cutting out the moldy area and replacing it with clean sheetrock.