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. 
These ways of making extra money cover a wide range in terms of compensation and prestige. Check out the options to see what could work for you, keeping tabs on a projected per-hour rate so you can see what would be worth your time. The list is loosely arranged by 1. jobs requiring more skill or expertise, 2. gigs needing less and 3. things you can sell. And if you think of any good options I missed, please let me know in the comments.
Referral fees aren’t just for the products you recommend. Perhaps the coolest thing about the Amazon Associates program is that you receive credit for any sale associated with your affiliate link for 24 hours. So, if a customer visits the page of the product you recommended, but then goes on to purchase five more eligible items during that same visit, you will receive a portion of that entire sale.
Hunt for under-priced used books that you can sell online. Download an app that reads ISBN numbers so you can scan the barcodes on books. This will pull up the book’s current price on Amazon so you can see if it’s worth trying to resell it. Then, visit used book stores, thrift stores, and garage sales to look for high value books. Post the books for sale online using sites like Amazon or Ebay.
People are turning to audio and visuals when it comes to technical subjects. However, you should consider doing an ebook first and turning it into an audiobook through a resource like Audible's ACX platform. You can hire a producer either through a royalty share program, so you don't have to shell out upfront cash, or you can do a pay-per-hour hire as well.
Cost per action/sale methods require that referred visitors do more than visit the advertiser's website before the affiliate receives a commission. The advertiser must convert that visitor first. It is in the best interest of the affiliate to send the most closely targeted traffic to the advertiser as possible to increase the chance of a conversion. The risk and loss are shared between the affiliate and the advertiser.