Musty air, damp joists and a quote for encapsulation.
What is under the floor, what moisture and mold signs look like, what encapsulation is and whether it is worth it. Recognition only; mold work goes to a pro.

What encapsulation is, when it is worth it, what a good job includes, and what it costs. , with what a fair quote lists.
Price per square foot, what changes it (drainage, sump, dehumidifier), and a fair total. Dated sources.
What a vapor barrier is, thickness in plain words, barrier vs full encapsulation, and price.
When a crawl space needs a dehumidifier, sizing, and installed vs unit price.
Floor insulation vs wall insulation in a crawl space, what goes wrong when it gets wet, and the price.
Open vents vs sealed crawl space, when each makes sense, and the cost of covers.
Where the water comes from (grading, gutters, plumbing leak, high water table) and the honest call for each; standing water near wiring is a call.
What crawl space mold looks like, what causes it, and when to call. Recognition only, never a remediation how-to.
What 'crawl space repair' usually means (moisture, sagging joists, failed supports), which needs a structural pro, and prices. No DIY structural work.