The two most common approaches to landscape are:
1. Showing, marketing, printing, & selling yourself.
2. Find an agency or stock house to represent your work.
I've done both and found that #1 was too time consuming for my taste. The business/marketing side is very time-consuming and you have much less time to shoot.
#2 has been the most profitable and rewarding. I shoot and upload the images to the agency and they do all the sales, promotion, and financial work. If you go this route, find an agency that fits your style of photography--they are not all created equal. For example, I do a lot of rural/agricultural work and my agency specializes in and has outlets for those types of images.
The biggest challenge you may face is determining if your work is really good enough to sell. For that, you may want to consider local competitions and portfolio reviews. Don't rely on the word of friends and family! Your photos may be good, but they have no idea how stiff the competition is in the real market place.