No doubt, you've been trackside enough in NJ and elsewhere to know you are not alone as a railfan with a camera. I've seen other railfans with everything from a cell phone to a point and shoot cameras to high end Canon or Nikon gear trackside.
The question in my mind is: Is there a demand for your what you're offering? How many other railfans that know how to take quality images have high end camera gear (myself included) have considered making a few dollars on the side selling images? Is the market saturated? Is there enough market to justify ones' time and efforts?
The problem is where to market your images. I've not discovered what the various RR oriented magazines may or may not pay. But I'm sure they get many images submitted for consideration and select precious few for publication, and sometimes it's a year or more before they use the image, unless it's a news item. A fair number of shots and a good article to go with it? You’ve probably got a winner. Various societies that publish calendars each year can always use a good image, but they are generally limited to donations, I suspect. The railroads themselves? I haven't seen any NS calendars, but the CSX calendar has all employee-submitted photographs on it. NS probably does the same.
So, perhaps the web is the best place to sell your pictures. But, how are potential customers going to find your site? Not to rain on your parade, but trying to be 'seen' is likely the biggest issue. Throw in the various internet forums that have more than enough images out there to suit most armchair railroaders’ desires. So what's left?
I've seen advertising here and there for CDs of rail-oriented images for sale. I haven't looked lately, but there's likely some CDs of images for this railroad or that railroad on
ebay almost all the time. The issue is pricing. Between
ebay seller fees and Paypal fees, there's 15% gone. Add in say, 30 minutes of your time to burn a CD and print the top of it with a nice image, etc. Cost of the CDs, sleeves or clear cases, packaging, USPS charges, etc. Maybe $7-8 dollars for a $30 CD is already gone, plus your time. And don't forget time to make postings, etc. Maybe make up batches of 5-10 CDs or (framed) prints and sell or consign them to some local model railroad stores. See if that gets some response.
My own guess is there aren't enough potential customers to pay, say, $50 for a 10x14 print, on archival paper, nicely framed. In years past, I've paid that for historical photographs, but I don't believe the 'market' is willing to pay that much these days. The sad truth is that any railfan with a digital camera can make enough prints to satisfy filling their walls with pictures. So unless you have a subject that a purchaser doesn’t have or can’t photograph themselves, the market is quite limited, in my estimation.
For what it's worth, I used to sell some excess items on ebay. What I quickly found out is that I spend just as much time selling/marketing/packaging $5.00 items as $300 items. I quickly learned to sell multiple low cost items together as a 'package deal'. So, it might take 3 CDs full of images for $25 to make a sale.  
I’d first look around at what other railfan photographers are producing/selling. You might even want to contact them and find out if they consider it ‘worth while’. I’m guessing you’ll find more lucrative uses of your photography skills doing weddings or engagement photography.