If you know a lot about some particular field, you might be able to carve out a unique niche by getting to know the professionals in your field who have expensive merchandise to sell. Seth is an example. He makes a great living buying, selling and promoting artists and their products that he locates through “starving artists sales.”
If you live in or near a city of any size, you have most likely have seen the advertisements for these. They are usually listed in the paper and/or are advertised on TV, especially the less expensive cable channels. The sales are held in a motel on weekends. There are hundreds of art pieces...
... and dozens of aspiring artists with paintbrush in hand.
Most artists, unless they are represented by a gallery or agent, don’t have a clue about how to sell their art. Act as a manager and promote or sell a particular artist’s work online or through the auction sites. And lastly, approach local art galleries to establish a business relationship.