How much may an amateur photographer make by selling photos online?

A photographer who gets paid (or intends to get paid) for his photos is a professional. Amateurs don't get paid!

How much you can get for them totally depends on how good they are along with your marketing. Famous photographers get a great deal of money for their photos. Give it a try and see if you can do well with them. Don't get discouraged keep going and trying different methods. Gallery showings, stock photos, most people I know who make money from stock photos have many thousands for sale along with video and cine footage as well. Peter Lik gets thousands each for his art quality prints, he has galleries in several major cities as well as online.

Without actually seeing your photos, it's not possible to say with certainty. Post a link to maybe a flickr page showing your images.

My best guess at this point is that your images wont' sell at all. Just because you use a DSLR doesn't mean anything. You could be using a $50,000 Hasselblad with a $5,000 lens and still produce junk images. Remember 90% of what makes an image great happens outside of the camera. You, not the camera, makes the image great. Your decision on subject matter, the lighting, composition, and the technical settings all combine to make an image great. The camera really doesn't matter that much at all. All of the technical and artistic training one needs to be able to produce good quality images that someone (other than your mom) would want to buy takes a lot of time. Most photographers have been at it for many, many years before they sell anything. You've been at for 6-7 months. Post a link to your images so that we can fairly judge your work and provide you with a realistic expectation.

Selling your images online is a good idea for many. Places like eBay, Craigslist, and etsy are a few places. You can also go to a local gallery and see what they say. My best advise to you is before you spend a single penny or single second on trying to sell your work, you must have it critiqued by a qualified professional. You should not and cannot rely on the number of "likes" or "thumbs up" that your work receives on social media. This is a great way of getting a false impression of your work. You must seek out a professional. One way is to go on photo workshop. While this isn't a cheap endeavor, it will be very educational.

But lets say you post your work on your online and it sells. From what I've seen at art shows in Northern California, an 8x10 will typically cost $7-$20 (unframed) depending upon the quality of the image and on the subject matter. You can have an epic image, but if it's of a subject matter that doesn't interest buyers, it won't sell.

Everyone has a camera these days (think cell phone). Everyone thinks their photos are great (think delusional).

How many photos have you purchased in the past 5 years? Why would anyone buy yours (or mine)?