If you want to clear some space out in your house and have a big stack of books you’ve been holding onto for too long, you can make money selling your books and textbooks online. Stores like Half Priced Books and others will give you cents on the dollar for each of your current books while you can check what your book is worth by simply entering the ISBN number on Book Scouter.
Buy and sell domain names. If you’re good at finding popular yet undiscovered domain names, you can make some cash on the side by buying and reselling websites. Think of it as digital real estate speculation. Domains are available on GoDaddy.com for as little as $2.99 per year, but are sometimes resold at far higher prices: According to Business Insider, the site MM.com sold for $1.2 million dollars in 2014. Once you find the perfect domain name to resell, you can market it on Flippa.com for a flat fee.
Research other listings in your city on AirBnB and see what the going rate is for a place like yours. You could also just rent out a private room as well or even a bed in a shared room. In fact, that's how AirBnB got its start. However, you might find it hard in the beginning without reviews, but as long as you take really good care of your guests and provide a lot of value, the reviews will eventually come rolling in.
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. 
To get hired, you fill out an application and take an exam to test your knowledge. “If you pass, you go through a mock session with an experienced tutor who assumes the role of student and evaluates your creativity, empathy and teaching skills,” says Cindy Hamen Farrar, Ph.D., senior director of academic tutoring at Tutor. “We look for people who know their subject matter and who can break it down and communicate effectively.”
Salvage and resell. Do you love antiques or have a knack for finding valuables at flea markets or yard sales? If you do, it might be time to consider salvaging items for resale – or even scouting out antiques to sell for a profit. While you’ll need to spend quite a bit of time searching for prospects and spend some money buying upfront, you could easily turn a profit if you know what you’re doing.
Mechanical Turk: Amazon's Mechanical Turk is a resource for doing human-intelligence tasks, or as the site commonly refers to them, HITs. You get paid a very small fee for any given HIT and you'll need a good deal of volume to make a substantial amount of money. But it is a resource you can use in your spare time to generate a small income online.
Proz.com is a site where you can get paid to translate all kinds of documents, including files and even conversations. The site provides you with an opportunity to list your services as a translator. They offer opportunities in Spanish, German, Italian, Chinese, Arabic, Japanese and other languages, and specialize in legal, medical, technical and other fields.
These mega-sites make it easy to set up shop so customers can browse your products, and there's no need to build your own website. Also, you’ll find a built-in search feature so that interested buyers can easily find your online storefront. Plus, you get to use the site's shopping cart. In short, you avoid a lot of the expense and hassle of setting up an independent e-commerce website.
20. Etsy – If you like to create arts and crafts, you can sell them on Etsy.It’s completely free to open an Etsy store. You simply sign up, post pictures of your creations and starting selling. You can choose your payment option, but PayPal is generally the easiest. Etsy makes it easy to sell and keep track of your inventory. There is a small listing fee and they take 3.5% of every sale you make.
If you offer freelance services or have a physical services business, then creating a blog is a must. On your blog you can write about the services you offer and how they will benefit your clients. Importantly you can add a ‘Services’ page, outlining the services you provide, what they include, and any other important information potential clients may need. This is an effective way to promote your services, generate leads, and increase your revenue.
Whether it’s an important consumer application, a specialist app to solve a particular niche problem, or even a time-wasting game you can play on your phone, you can create a massively successful business if you build software that helps people. (Look at the rise of Slack—the team communication software that went from side project to billion-dollar company in just 2 years.)
If you don’t mind doing other people’s chores, then TaskRabbit is a great option for making money online. Earn extra income by walking your neighbor’s dog or mowing Mr. Smith’s lawn. It might seem like not the most lucrative option, but the top taskers reportedly earn as much as $7000 a month, making this a full-time way to make money online for some.
High-ticket consulting or coaching: You could sell your own high-ticket consulting or coaching products from your website. You'll still need a website, merchant account, sales funnel, lead magnet and many other items. But you can easily earn a substantial amount of money from each individual customer, making it well worth the arduous setup required.
23. Affiliates – There are many affiliate networks, such as FlexOffers and CJ Affiliate that allow you to promote other people’s products and services. You simply put a link or a banner on your page and then you get a percentage if someone clicks through and buys the product/service. You’ll want to select products that are specifically within your blog’s category.This is an effective way to earn money once you have the traffic coming to your blog.
Focus on the surveys and offers at the top of the list. Here's a tip not many people know. CashCrate has a special algorithm that automatically selects the best surveys and offers and places them at the top of the list. There are several factors that go into determining which are the “best”, including payout, approval rate, and a variety of other factors. But all you need to know is that these surveys and offers are great, so you can do them in confidence!