The FAA requires all drone operators flying for what it deems commercial operations must pass the Part 107 Knowledge Test or risk being fine. Real estate agents hiring a non-licensed drone operator risk fines upwards of $11,000. Agents that are also unlicensed drone operators face even greater fines.
If you operate a drone for any use deemed by the FAA as commercial use without this qualification, you are also subject to large fines if caught.
A person operating as hobbyist as defined by the FAA are not required to obtain this qualification.