MOLD, that ever present problem that both Landlords and Tenants have to face. First, it is important to understand that how the mold becomes present depends on who is liable. For example, a tenant that does not properly vent the bathroom, such as during showers, when a landlord requires such, if mold develops, it is on the tenant to remove the mold.
Now, where to start? The EPA has valuable information regarding mold that will give you some basic understandings. I recommend that you start there (http://www.epa.gov/mold/index.html).
With this understanding, there are many ways to treat mold. The traditional way has always been with bleach. This is not recommended anymore. For tenants, if you use it and it drips on the carpet causing a stain, you are now liable for replacement of that carpet. For landlords, if you advise this course of action and a drip occurs, then you become potentially liable. Bleach is also not recommended now because many molds have mutated, building up a tolerance to bleach and making it ineffective.
So, what do you use? There are many mold killing agents available such as Zinnser Perma-Wash and X-14. These are actually more effective at killing mold than bleach anyways.
Here are some recommended steps to cleaning the mold. Before getting started, always make sure to use proper protection and properly ventilate the area:
Spray a towel/rag with the cleaning product. DO NOT spray the wall because it will cause the spores of the mold to become airborne making the environment unsafe. Then wipe the area, fold the towel, re-spray the towel and wipe again. Keep doing this until the surface growth is gone.
Next, take a soft bristle brush and warm soapy water and gently clean the surface. Do not saturate the surface or it can just lead to more problems (ie. more mold). This is just to get down to the surface. Then use a towel/rag and dry the surface. After cleaning, a stain may still exist.
Once dry use a spray shellac over the area. Shellac is alcohol based that will dry quickly. The purpose of this is to seal the odor from the mold growth.
Once dry, use an oil based primer, such as Kilz, and spray/paint the area. This will seal in the area from further growth.
Now you can paint. It is recommended that the paint contains a mold inhibitor. It can be added when the paint is mixed and can help prevent future growth.
Now that you know what to do, stay on top of this. Landlords, make sure you address this quickly. Do not be cheap and use the easy route either. This route can only lead to a lot more cost than it should have been. Tenants, make sure to keep your landlord in the loop. Get authorization for the paint. Sometimes, the landlord may have the supplies for you.
Mold is dangerous. It can cause many health problems that can easily be avoided. When you discover it, act quickly and you will not only keep the unit safe and healthy but you will save a lot of money.