Better yet, you can even upload your own book to one of the world’s largest book sellers: Amazon. With Amazon self-publishing, you set the price, retain the rights to your book, and get access to Amazon’s massive audience. For every sale, you keep 70% with Amazon taking the remainder as a fee. If you want to get started, check out Leslie Samuel's great guide to selling eBooks online or follow Tara Gentile on CreativeLive as she shows you how to use your existing body of work to write an eBook within the next week. Who knows, you might just write one of the best business books of this year!
You can sell product from your own website store, via community sites and classifieds (like Craigslist) and of course eBay and collectively make good money. The challenge, like with any business, is defining what is your competitive advantage and can you come up with a model that meets your needs. For me selling physical product was a great proving ground, but I eventually learned that profiting from information was a preferable model if I wanted to meet my aforementioned business goals.
Udemy is one of the world's largest platforms for selling online courses for just about any topic or subject. As long as you have the proper skills, you can likely teach those skills on a platform like this. However, don't expect it to be easy. Fierce competition means that you need to deliver loads of value and expertly market your course online if you're going to make any respectable amount of money.
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. 
Sell stuff online. If you have high-quality items to sell, there are a slew of online marketplaces you can use. Just make sure you understand the fees associated with your sale before you take the plunge. Where neighborhood Facebook pages and Craigslist ads are free, many online marketplaces or consignment shops charge for ads or require you to fork over a percentage when you make a sale.
One factor that you must be aware of though is that Care.com is a peer-to-peer arrangement. That means that you will be in direct competition with other pet sitters in your area. You must price your services competitively in order to get business. Once you begin to develop a list of regular clients, you will be in a better position to raise your rates. This will be particularly true as you get referrals from those customers.
If you’re willing to take on some risk and have the heart of a true hustler, you can make extra money online doing commission-only sales for startups and other businesses. While you won’t be getting a regular salary, with the right sales strategies and skills as an inside sales rep, you can make decent money for each sale you bring in. And because you’ll most likely be working with startups, if you can negotiate a little equity you could profit big time if you're pitching a solid product and the startup succeeds.
Daily Surveys can be taken one or more times per day. This is indicated in the survey description. Other targeted surveys can be taken as you see them. Be sure to complete these when you see them. Some surveys may accept a limited number of responses from people matching your demographics, and can sometimes disappear quickly. New surveys come out all the time too!
Earn cash back for shopping. Earning cash back on your purchases is a smart idea, and credit card rewards aren’t the only good cash-back strategy out there. With sites like ShopAtHome.com, eBates.com, and TopCashBack.com, you can earn up to 10% cash back on purchases made with approved merchants. Many frequent shoppers also love the Ibotta app, which lets you earn cash-back on every purchase.
How many hundreds (or thousands) of dollars of stuff sits in your garage? Maybe you have an attic or off-site locker. You might be keeping these things to use “someday.” But, let’s be honest. If you don’t use something in five years, you should sell it. You might think it’s worthless junk. But, as the old saying goes, one man’s trash is another man’s treasure.
Using a food delivery service can’t necessarily earn you money, but it can help you save you money if you constantly find yourself throwing out half the food you buy. Food delivery services send a box of food every week with new, sometimes unique vegetables, meat, fruit, and so on. If you don’t have time to shop and want simple meal-prep that leads to a good meal, a food subscription service may be perfect for you.