If you are getting paid when using a drone … commercial use … you need approval from the FAA. You could get fined $1,100 (or more) for operating your unmanned aerial system (UAS) for business purposes without FAA approval. You can apply for your very own license by passing a multiple-choice test and paying a small fee. No experience is necessary! The FAA will provide a Remote Pilot Certificate after training and testing.
I have only talked to a couple of field inspectors using a drone for commercial inspections.