Moisture Comes First, Always
Without moisture, mold cannot grow, which is why cleaning it up while the leak continues just resets the clock. Typical sources include a dripping trap under the vanity, bad window flashing, a bare-dirt crawlspace, or a bath fan exhausting into the attic.
A good remediation scope names the source and either includes the repair or tells you who needs to make it. If the problem is a plumbing leak or roof flashing, a plumber or roofer may need to come first.
Dispatcher tip: Make sure post-remediation testing is done by an independent assessor, not the same company that did the work. Buyers and their agents tend to trust that report far more.