Examine the work of the great photographers at the local library
Ansel Adams and Eugene Smith produced dissimilar images using similar skills and techniques. Their portfolios are accessible and educational. Adams focused on landscapes while Smith was a photojournalist, but their collections contain commercial quality images, which are inspirational and instructive.
Check out the work of photographers currently producing commercial quality images. Adams and Smith produced their work years ago, but the most recent great photography is available at libraries and museums. Successful photographers showcase their best images on their websites and market their work to the public.
Narrow the focus of your research to the work of photographers who share your interest in subject matter.