It would be great if a landscape photographer could make a living just shooting and selling prints. First off, you'll have to do promoting like other APUGers suggest to build your reputation. Once you have a reputation, you'll probably have to teach via workshops, a faculty position at a university or at a college. Other sources of income are stock sales and commercial work. I went to a talk by Michael Kenna and was inspired by his work. I saw some of his work at the Wirtz gallery in San Francisco and saw his 8x10 prints for sale at $600 each. Minus the gallery commission, he'll probably get get $300 at best. He also does commercial jobs. Here's Mr. Kenna's site.

http://www.michaelkenna.net/

Stephen Wirtz site: http://www.wirtzgallery.com/main.html

Good luck!
Don