Buying a drone is easy. Flying one for business - not so much.
As a certified drone pilot, I often get asked if I "really need a license to fly."
The answer is almost always yes.
Here's how you check for your pilot's credentials.

Check the Airmen's Registry
The FAA maintains a list of all pilots and their registration in an easy to check out list. This list is located at https://amsrvs.registry.faa.gov/airmeninquiry/ and pilots are located on it by name, address,pilot number and other identifiers. When signing up, the pilot can opt out of everything except their certificate number and name, so sometimes they can be hard to track down. My certificate number is 004300408. Can you find me there?
Of course Pilots also carry a card similar to your drivers' license, and can provide that when asked too.
With the Remote pilot Certification, the pilot has to Recertify every 2 years. This information is less easy to track and the best way is to ask the pilot for their Recurrent Certificate. This is a credit card size paper or a full sheet certificate.
Unlike the TRUST certificate for hobby flight, the Remote pilot certificate allows the pilot to fly "for profit" or in ways that could be "for profit."