Instagram does not offer anything on their own to enable their users to sell their photos. Hashpix has launched a platform for the same.
The company states:
Hashpix is the first marketplace where fans can buy photos from the best Instagram photographers. These are only the top Instagram users so you can own the best Instagram photos.
The company handles the complicated tasks like processing orders, printing photos and delivering them to the customer. Users get 70% of all profits.
The service however has a requirement if you plan to join their platform:
You should be an active Instagram user with a large fanbase that likes and comments on your photos. You should be an active user of social channels including Facebook, Twitter, or Tumblr.