Well, there are few uses for a digital photograph sold to average consumers. Sure, companies purchase photos -- but the digital uses of your photos for average people don't extend much farther than desktop backgrounds, and quite frankly, if they want a picture like yours for a desktop background, there's a good chance they can find something similar out there -- but a better image with better quality, and free.
Other than desktop backgrounds, most people don't have a specific need for digital photos. Printed photos, sure -- but if they like your photo enough to buy it, chances are they want to buy a print of it. Not a digital to print themselves.
The other struggle with this is that when you're selling purely digital images, it's pretty easy for them to just right click and save it. Chances are whatever they would use it for isn't worth paying for, especially when there's better stuff out there for free.
Now, let's presume for a moment that you CAN find a buyer. It depends on a lot more than that the image was taken with a D40 and is "very high quality" -- the camera doesn't mean a thing in terms of how good a picture is. Some cameras are better as a recording medium than others, but a crap photographer will produce crap photos no matter what they use. It depends more on how good your images are, what the images are of, what rights you're selling, etc.
And as for rights...that will open up a whole new can of worms for you. Will you have a contract? Will it be a faxed and signed contract? Will you not have a contract, and therefore screw yourself over by just selling them the image for a set price with no determined guidelines on how they can and cannot use the photograph?
Now, if you mean commercial purposes, i.e. companies, you first need to get over the road bump of the fact that companies don't go to sites like Etsy for their images, THEN you have to open up the even BIGGER can of worms that is the issue of copyright in a commercial setting.
All in all, I think you're getting pretty far ahead of yourself here.