Contamination with mold is one of the worst things that can happen to a house. In addition to structural damage, the inhabitants can face rather severe health problems before the mold is even detectable by odor. To a human, that is. Dogs can be 800000 times as sensitive to odors as humans and they can be trained to detect many species of mold quite accurately, although the large number of harmful mold species means that a dog may not be trained to detect all of them, but maybe only the most dangerous or common ones.
Nevertheless, an inspection by a mold dog can be one way to assess whether a house you think about buying is really worth the money. Mold contamination is often a sign of moisture problems, which can be quite difficult to fix, if the house has been built improperly.