Amazon launched back in 1994 and, two short years later, they developed their Amazon Associates program. In so doing, Amazon was able to increase exposure to their marketplace by enabling web developers and site owners to work as evangelists for their products. It helped drive more traffic to Amazon while giving these business-minded individuals the opportunity to generate more revenue for their own sites and businesses.
Note: I think the line where readers will push back probably will vary from blog to blog depending upon their readership. For example here on ProBlogger I get a little more negative feedback from readers on affiliate promotions. I suspect ProBlogger readers are a little more tuned into the issue and suspicious of some of the affiliate marketing that goes on around the web.
Webinars are quite possibly one of the most potent ways you can make an exorbitant amount of money online. You'll need an audience to train and you'll need to know what you're talking about. Of course, this usually requires having a website and some semblance of an online presence. However, people can still do webinars without all of that. For example, you might have a sizable social media following and you train them every week on something to do with social media. But you will need a product to embed and sell at some point. Don't worry about it in the beginning. In my experience, the best webinar platform out there is GoToWebinar.
Fiverr is one of the biggest providers in the gig economy on the web and you can sell a wide variety of services and products through this medium. Do the research and find out what you can offer. However, keep in mind that like any other money-making task, it takes time to succeed here. And stellar reviews will help you generate more and more income over time.
Music may perform better than books and other products, mainly because you can listen to the clips of an entire album in roughly 10 minutes and get a good enough feel for it without buying it to write a short review. If you have another topic that you're passionate about, great, but make sure you have a unique angle on the topic. People can get reviews about a lot of those consumer products anywhere. You need to give them a reason to visit your site.
It’s extremely WordPress-friendly. As you’ll soon see, it’s very easy to add Amazon affiliate links to WordPress. If you decide that you want more than just the occasional link to appear within your content and you want to build an entire affiliate store, there are WordPress affiliate themes and plugins built specifically for Amazon Associates members.
Also known as a publisher, the affiliate can be either an individual or a company that markets the seller’s product in an appealing way to potential consumers. In other words, the affiliate promotes the product to persuade consumers that it is valuable or beneficial to them and convince them to purchase the product. If the consumer does end up buying the product, the affiliate receives a portion of the revenue made.
When I used to write product reviews, I used to include just one affiliate link. For some reason, I thought that a single link would be enough and I didn’t want to run the risk of annoying readers with more links. However, one day it struck me that the reviews I was writing were quite long and by the time people got to the end of them, the link to Amazon was no longer visible.
Find a profitable niche. Starting with your interests, write down as many niche ideas as you can. Think about topics people might search online. Ideas include passions (like surfing or body building), fears (like spiders or speaking in front of crowds) and problems (like getting out of debt). Do keyword research to see it others are interested in the topic. Find out if a domain name is available that matches the keyword 100 percent. 
If you live in an area where Uber or Lyft operate, why not become a driver? If you're looking to make some short-term cash, you can definitely rake it in by working for one of these popular car-hire apps. As long as your vehicle fits within the specifications of their program, and you have a clean license, you could do this on the side, especially if you're in a crunch for cash.