Are you selling through Amazon? Does it become a reasonable income at some point (i.e. if you create enough stories for them to drip drip drip income)?
Amazon, iTunes, Barns&Noble, Google Play, Kobo, Smashwords and a few others.
When ebooks first came onto the market it was possible to make good money just by pubbing, and I know people who made a lot that way. I caught the very tail end of that and made good money for one month and then the moral panic about ebook erotica wiped me out. (Apparently, my stories are 'just like heroin'.)
The amount of technical skill required to self-publish is fairly low. I think most people could learn the ropes well enough in a year to write competitively, even if they've never written before. The closer your writing matches mainstream tastes and expectations the better it will sell, of course. (That's always been a challenge for me.)
The main problem is discoverability. More stories means a greater chance of someone finding your work (just like tickets for the lottery) and more potential income streams. But since anybody can publish these days, because the barrier to entry is incredibly low (much lower than, say, making music or video games), your competition is basically all of social media. I know writers with hundreds of stories who aren't making enough to cover their phone bills. I have several dozen novels/stories and make a couple hundred a month. (I've been writing for 7 years.)
I was on a forum with a bunch of writers who were making six- and seven-figure incomes (they got into it early, but they'd moved on from erotica by then) and they were adamant that the only way to make money these days was to spend a lot on advertising. It was pretty much all they talked about, and they had budgets of several thousand dollars a month set aside for it. So ... if you have a lot of money, it's possible to make a lot of money. (Quelle surprise.) They also advised people to publish a novel a month if possible, since readers have short attention spans.
The other way to get readers is to be popular on social media. (Or famous irl, I guess.) If you look at the indie writers who 'come out of nowhere' and make a lot of money, they almost always had a large social network before they even published. A lot of them were very active on fanfic sites. (So a lot of immediate readers who will give them five-star reviews.)
If all you want is a bit of extra spending cash, you can do that by self-pubbing, but it will still require a bit of work and patience. (I made $2 the first month. Like I said, you're better off panhandling.) But if you want to make a lot of money, short of some kind of fluke, you need to be rich or popular. So get good at social media. (Just don't let it cut into your writing time too much.) On the plus side, you don't really need to worry that much about the quality of your writing unless you're trying to get an agent or sell a manuscript to a traditional publishing house.