I literally went from $20k/year to $150k/year in 2 years – see my 2018 income reports. I did this by dropping my web design/SEO clients and tried to make money with affiliate marketing (I write SEO/speed optimization tutorials). 90% of my affiliate income comes from SiteGround, a hosting company who awarded me affiliate of the month in July, 2017 when I made $9k in 1 month. Since then I have continued to hit numbers like this – the screenshot below is from March, 2018 when I made $14.5k in 1 month (just with SiteGround). I have other affiliates too.
Thirsty Affiliates tracks, cloaks, and categorizes your affiliate links. Once you’ve signed up for your program(s) grab your affiliate links and add them to this plugin. This can take time if you will be linking to multiple pages on your affiliate’s website (which in many cases, you should). The pro version comes with statistics but I don’t even use it and I’m quite the analytical person.
This domain can work for people in two ways. One is to get sudden bursts of income by selling a certain product. The second part is selling a service that gives you recurring fees. This course on Affiliate Marketing Strategy for Stable and Recurring Income can be very helpful if your objective is the latter. At 5.5 hours and 56 lectures, this is very extensive and useful for those looking at mastering this subject. Details are available here.
If the answer to each of these questions is a resounding yes, rather than jumping to conclusions immediately, take time to research whether or not others are out there making a sustainable affiliate income from products and content in this niche. In a sense, competition is a good thing here—it'll help you validate your idea and prove that it's worth of building a business around.