What’s the catch? None, really. Cash back apps act as affiliates for many online merchants, which means that whenever you make a purchase through one of the apps, they get a small commission — but then, they give you a portion of that commission as “cash back”. For example, if I buy a pair of Nike shoes through the Ebates app (or website) and spend $75, Ebates may get a $10 commission but then they’ll pass $7 back to me. It’s basically a way to get sale prices on stuff that isn’t on sale!
For those with a large Twitter following, you can make money from your Tweets alone with Sponsored Tweets. You could be paid for sharing a business’s information, recommending restaurants or hotels, or tweeting pictures of you using or wearing products. As with all sponsored posts on social media, businesses will only be prepared to pay you to Tweet if you have a large following that you can influence. So work hard on building up a loyal fan base.
Amazon will have you work on micro-projects that require some sort of human interaction. Tasks can include translating a paragraph into English (or another language), rating the search results for certain keywords, or reworking an article. The tasks are simple, and you will be paid a small amount to complete each. But if you do enough tasks quickly, you can make a respectable amount of money.
Prior to that group, they had an online community for teachers looking for lesson plans. That probably sounds pretty random, but it's crazy the type of communities you can build and rally people around. If it's something that you're passionate about yourself and you want to connect with others that have that same passion, then an online community is something you should definitely consider.
However, not matter what method you choose to make money online, understand that you might be able to make some money fast, but for the sizable returns, you'll need significant sweat equity. However, a year from now, you'll be happy you started today. Remember, time is far more valuable than money. Focus on creating passive income streams that will free up your time so that you can quit the rat race and focus on the things that matter. That's the important thing here. 
If you have nothing of value to sell from home then retail arbitrage might be a better option for you. Many people partake in arbitrage to earn a little extra money, and for some it has even become their full-time job. Retail arbitrage is the buying of goods at a low price and then selling them on a different platform at a higher price. Sales in shops provide ideal opportunities to pick up products for next to nothing. These can then be sold on eBay or Amazon for higher amounts, making you a nice profit.

You can work as a virtual assistant through dedicated websites, such as Upwork or Zirtual. All kinds of skills are needed, and compensation can vary anywhere between $10 per hour to $100 or more. Obviously, the higher pay will be to people who have more technical skills, such as web building skills and marketing. But you can find work doing administrative tasks at the lower end of the pay scale.

It’s something akin to picking stocks. You want to buy undervalued domains, and sell them later on at a higher price. For example, you can pick a domain that is out of favor, but could be related to some future event. So if you decide that the stock market is likely to crash in the future, you can buy a domain that includes the words stock market crash during a rising market, and then sell it in a falling market.
Here’s a good example of how lead sales can work in real life: My second website, Life Insurance by Jeff, brings in a ton of traffic from people who are searching the web to find answers to life insurance questions. While I used to have the website set up so I could sell these people life insurance myself, it was a lot of work to process all the different requests and clients. As a result, I started selling the leads I gathered instead.