In commercial and multi-family buildings, the question is rarely just 'is there mold'. It is which unit, which mechanical zone, and who is responsible.
Shared HVAC changes the sampling strategy: a source in one suite can register in three others downstream of the same air handler. Sampling has to be planned around the mechanical layout, not the floor plan.
Sample counts scale with square footage and with the number of distinct air zones. For larger properties we scope the count on site and price additional samples transparently at $75 each.
Documentation is the deliverable. Property managers, insurers and counsel all need a report from an independent third party with laboratory backing, not a contractor's estimate.