Photography was always a niche market, but in the days of film a photographer who could consistently take excellent shots could make money. Hiring a professional photographer was a bit costly, but there were times people would pay the cost.
Digital cameras have decimated the market for many professionals, except perhaps for commercial and architecture, which require specialized equipment. A person with a camera no longer needs to know how to use a light meter to ensure a properly exposed negative for an image they can't come back and recapture. A digital camer let's the user see what they have and in many cases reshoot. Not always.
People are taking their own pictures because its cheaper and easier. Paying for a photograph is a luxury which is difficult for the average market to bear, momentarily.
If you wish to make the attempt, beside the printer you'll need a computer and image editing software such as Photoshop. A tripod, for multiple exposures to increase the exposure range in situations you can't control the lighting, an external flash eventually ( so make sure your camera can support one) and, if you're going to photograph people, a portable reflector.
You have to make your images better than everyone's around you, of you're going to,sell them.
Here's a free site that runs digital photography competitions for fun, and everyone rates each other. I used to be one of the critiquers , for people who wanted an in-depth critique of their photo. You can learn a lot here and get a reality check. It's got a LOT of members. Generally five or seven competitions going on at a time and hundreds of entries per competition. They are also time limited. You must take the photo AFTER the competition was announced, and taken specifically for that competition. Again, it's free.
Http://www.dpchallenge.com