Matched Betting (not available in the USA) enables you to gamble (nearly) risk-free. I say nearly as there is always room for error! It involves placing bets on all outcomes of an event, using free online bets given out by the Bookies. Although it may take a while to get your head around the concept, Matched Betting can make a substantial addition to your monthly income.

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.
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. 

Will my target audience realistically buy this now, or at a different time? Be sensitive to sales cycles and seasons. Maybe you should avoid holidays (when people are away from their computers, like July 4 in the U.S.) or maybe you should target holidays (like the day after Thanksgiving), but know the difference. Again, know your audience. Plan your content accordingly.
Online advertising started to take shape – Cost Per Mille (CPM) models and paid placements were important components of the marketing mix, but difficult to measure. An emphasis on quality traffic and conversion helped transition marketers from buying impressions and site visitors, to paying exclusively for traffic that resulted in a sale and affiliate marketing lead the charge.
Signing up with Google AdSense will enable you to make money from advertising on your blog. Google AdSense will place relevant ads around your site, and if your site visitors click on these ads, you will earn a fee. Although each click only amounts to small change, if your blog has high levels of traffic, this will quickly amount to a reasonable sum.

MemberPress is a feature-rich plugin that will enable you to turn your WordPress blog into a fully functional membership site. Depending on how you want to run your membership site, you could have a mixture of free and premium membership plans. Premium plans could include no adverts, free downloads, access to extra content, membership forums, and much more. However, it is important to remember that if people are going to pay to view your content then it must be high quality. Otherwise your members won’t renew their subscriptions when the time comes.
Affiliates were among the earliest adopters of pay per click advertising when the first pay-per-click search engines emerged during the end of the 1990s. Later in 2000 Google launched its pay per click service, Google AdWords, which is responsible for the widespread use and acceptance of pay per click as an advertising channel. An increasing number of merchants engaged in pay per click advertising, either directly or via a search marketing agency, and realized that this space was already occupied by their affiliates. Although this situation alone created advertising channel conflicts and debates between advertisers and affiliates, the largest issue concerned affiliates bidding on advertisers names, brands, and trademarks.[35] Several advertisers began to adjust their affiliate program terms to prohibit their affiliates from bidding on those type of keywords. Some advertisers, however, did and still do embrace this behavior, going so far as to allow, or even encourage, affiliates to bid on any term, including the advertiser's trademarks.
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.
Find work. When you first start out, you may have to accept work writing about a topic you don’t find all that interesting. You must keep an open mind and be willing to accept work that may not be in your desired field. However, as you continue to write, you not only learn about more topics, but you also build your reputation. With time, you can be choosier about assignments you want to accept.[19]
Travel blogging is a hard industry to break into. However, the rewards can be worth it, and let’s face it, who doesn’t want to be paid for traveling around the world! There are numerous ways to monetize a travel blog, but affiliate marketing should predominantly be your focus. On your blog, promote hotels, tours, equipment hire services, flights, and anything else travel related. Then take a cut of the proceeds as your audience books their holidays based on your recommendations.
Because of the strong interest in quality of life and work-life balance issues, life coaches have become popular in recent years. Unlike the intellectual demands of becoming a technical or executive coach, life coaching can be successful if you possess common sense, a respect for family and a commitment to enjoy life to the max every day and helping others do the same.
Market your course: The beauty of using a course to make money online is that you can continue to sell it for as long as you’d like. Look for niche communities on Facebook, LinkedIn, or Reddit that might benefit from your content. Guest post on relevant blogs and sites. Look for anywhere you might be able to get in front of the right people. With just a few hours a month you can continue to generate sales.
If you're serious about making money online, start a blog. Blogging is one of the easiest and most sustainable income sources. As long as the blog is setup the right way, in the right niche, with the right content targeted at the right audience, and the offer is complementary to the content, you could make a tremendous amount of passive income from a blog.
Find an audience for your passion or hobby and you’re all set to make money online doing something you love via a niche website. That of course, is easier said than done. Creating a profitable niche website takes time and is not intended for the faint of heart. But, if you can hurdle the steep challenges and positively answer a few key questions on whether the website business idea you’re thinking about is profitable, then you can begin building it and eventually monetize through advertising, affiliates, or other relevant products.
In 2006, the most active sectors for affiliate marketing were the adult gambling, retail industries and file-sharing services.[17]:149–150 The three sectors expected to experience the greatest growth are the mobile phone, finance, and travel sectors.[17] Soon after these sectors came the entertainment (particularly gaming) and Internet-related services (particularly broadband) sectors. Also several of the affiliate solution providers expect to see increased interest from business-to-business marketers and advertisers in using affiliate marketing as part of their mix.[17]:149–150
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