One: get it documented
Write down what's visible, hold off further damage if that's safe, and capture the relevant history.
Two: look past the surface
The visible mold is only one clue -- water entry, humidity, material condition, containment, and post-work verification round out the plan.
Three: put the scope on paper
Preparation, protective steps, materials, access, permits, testing, cleanup, finish restoration, exclusions, and change-order rules should all be in writing.
Four: weigh your options
Confirm credentials, then compare the reasoning and limits behind each proposal, not just the total cost.
Five: check the closeout
Confirm testing, cleanup, paperwork, warranties, and any remaining maintenance before considering the job done.