1) Meth lab--no, there is no obligation to disclose the past uses of a home, including criminal uses. The exception would be if there was some reason to think there might be either some residual hazard or threat (e.g. dangerous chemicals about) or that the illegal action has or could lead to a legal claim affecting the home (for example, it is sometimes possible for the state or the federal government to seek confiscation of a home used in a criminal enterprise).2) Black mold--you need to check your state law (you do not indicate your state in your question) to be certain of what is required as a disclosure, but in most states, disclosure of a previous mold condition is not required unless there is some reason to think it currently does or may constitute a hazard or threat. But if it was fully remediated in the past, disclosure would not seem to be required.