Establish a portfolio of work. Make digital copies of your portfolio which can then be uploaded to various online art markets.
Join a print-on-demand artist market. There are numerous such markets available, including finerworks.com, artistrising.com or fineartamerica.com.
Upload your original art to the print-on demand marketplace. Individuals will now be able to download your images onto prints, calendars, or various other memorabilia, and you will receive a royalties for the use of your work.