It is important that people have a full understanding of the health dangers of mold and how to properly remove it...NOT all molds are toxic however research has confirmed that they all cause different health issues the most common is chronic Allergies especially in the very young and the elderly..
I'm a mold certified inspector any questions ask me free @ my new questions and answers website, see the link below
Usually the buyer will rely on their home inspector and their own visual inspection to look for any water intrusion or mold. If anything is noted, the buyer will pay for a test.
The actual mold test usually entails taking an air sample inside and outside a home. Mold is everywhere. What the test looks to see is if there is a higher concentration inside the home as oppossed to outside the home. There are not accepted levels of mold. If their is a higher concentration inside a more invasive inspection will look for the source. The inspectition and samples can cost $400-$800. It is not cheap.
If visible mold is found a swap sample is taken to see if any is considered toxic, but the real issue is finding the water source that is allowing the mold to grow. Once the water intrusion is found and rectified the mold damaged drywall or wood is removed and the room can be cleaned with big filters.
Truth be told, most mold can be killed with a $2 spray bottle and some bleach solution, but no one makes any money with that so they sell you on a $10,000 remediation with big air filters that run for a day or two.
There was a huge amount of public awareness of the mold issue that has waned. It is still an issue that we all look for, but buyers are relying on their visual inspection and their home inspector to first find any signs of mold before they spend a bunch of money on a test.
My mold inspector is Bob Senel his website is http://www.MoldinCalifornia.com, yup I go to the guy who actually wrote a Book on the subject of mold!