What are the terms of the program? Is there anything I need to be aware of that would make a program not worth it for me. For example, Amazon Associates does not allow you to put your affiliate links in emails. If your main method of communication with your audience is via email, Amazon might not be a good fit for you. Wayfair, for example, does not allow their affiliates to post affiliate links on Pinterest or any other social media site. If that’s a strategy you rely on, Wayfair might not be a good fit for you.
I'm just starting at Clickbank, so I'm a total newbie, but if I want to follow this strategy can I do it promoting just one product, for example, Category>Health & Fitness ---> X product. Then, should i start a blog or something like that where i can talk about things related to the product subject? if so, do i have to start making entries about this recurrently? or I can opt for just making an article with a free ebook in exchange to user's e-mails and follow the process?

One thing alot of ppl don’t know is that their small blog and writing about things that are passionate to their heart can yield them healthy affiliate income vs what they’re earning on the day job now in as little as 2 years. The key to success in affiliate marketing if you’re generating income via a content-based WordPress blog or static HTML website is to frequently update it with “lots and lots of content” Transformational content marketing in a specific niche is possible for anyone who has 0% experience writing online.
You don't have to be a professional photographer to sell your photos for money. People are constantly in need of high-quality, unique stock photography for websites, presentations, brochures, and so on, and are willing to pay for the right image. People generally search for images on stock photography sites, like ShutterStock, Dreamstime, and iStockphoto by keywords, not by photographer name, so you have the same chance as anyone else of having your image selected. Just be careful that you don't have images of trademarked brands, copyrighted art, or people's faces that are readily identifiable unless you have a model release - virtually anything else is fair game.
2nd tier.  If you are an affiliate for a particular program and you refer others to sign up for that affiliate program, a 2nd tier program will pay you when the affiliates you referred make sales. For example, I am an affiliate for Ultimate Bundles. If you join their affiliate program via my 2nd tier affiliate link here. I will get a small percentage of any sales you make going forward.
With drop shipping, you’re effectively partnering with a manufacturer or wholesaler to sell their products. This way, you don’t pay upfront costs to buy inventory, aren’t sitting on unsold items taking up expensive warehouse space, and don’t have to deal with shipping the products yourself. You simply create your site, fill it with drop shippable products, and drive in customers, with almost everything else done for you.
No matter what method you select for generating your online income, there's one very important thing to understand. Today, across this globe, with its 7+ billion inhabitants, there are two recurring things that people are looking for more of. Either people want more time or they want more money. The truth? Time is far more valuable than money. You can't recreate time. Once it's spent, it's gone forever. Not money.
If you have graphic design skills then you could make money online by creating and selling your own design elements, like templates, fonts, graphics, and other assets. This is a great way to earn extra money, and build up a portfolio of work, which could lead to you picking up freelance graphic design jobs. Websites like Envato Elements pay you a fee per element sold, which can become quite profitable if your work is popular.
Long-tail keywords are search phrases, rather than one or two words. If you are planning to promote an online poker course for example, you might do some keyword research and decide that the term "online poker course" has too much competition from existing websites, but articles based on things like "When to push during a sit-n-go" don't have as much competition and may yield more traffic.
ClickBank allows each vendor to determine the appropriate return, replacement or cancellation policy for its products (each a "Vendor Return Policy"). See the Client Contract (Section 3(a)), for more information. Each vendor will make its Vendor Return Policy readily available to customers prior to purchase of a product. If the applicable Vendor allows for returns, replacements or cancellations, ClickBank will allow for the return or replacement of any product purchased using the ClickBank services in accordance with the applicable Vendor Return Policy. For recurring billing products, returns for more than one payment may be provided if requested within the time stated in the Vendor Return Policy.
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. 
There are many freelance options for graphic designers who are looking to make money online. Designing layouts and graphics for promotional material, corporate reports, magazines or book covers, are all tasks that businesses are looking for online freelancers to complete. Due to its flexible nature, graphic design possibilities can range from one-off projects, to ongoing work with regular clients.
ClickBank is the Web's most trusted Digital Marketplace. ClickBank is a secure online retail outlet of digital product for vendors and active affiliate marketers. It is stated that ClickBank makes a sale somewhere in the world every three seconds by safely processing numerous digial transaction a day. Also, it serves more than 200 countries and is constantly ranked one of the highest traffic sites on the web.
A fitness site can have numerous revenue streams. Create healthy eating plans and recipes and lock them away as premium content. Promote and sell a fitness training course, eBook, or a series of videos. Or advertise your own personal fitness services on your site. Topfithub is  a good example of a fitness site with decent video content alongside product reviews.

One thing alot of ppl don’t know is that their small blog and writing about things that are passionate to their heart can yield them healthy affiliate income vs what they’re earning on the day job now in as little as 2 years. The key to success in affiliate marketing if you’re generating income via a content-based WordPress blog or static HTML website is to frequently update it with “lots and lots of content” Transformational content marketing in a specific niche is possible for anyone who has 0% experience writing online.
Win-win-win. The advertiser wins because they only pay when a purchase is made (as opposed to the shotgun approach of paying to advertise to the masses and waiting for a small percentage to actually buy). The affiliate wins because they make money while providing helpful advice. The customer wins because they get a trusted recommendation for something they might not otherwise have known about.
If my piece of content is so unique and valuable around hiking backpack recommendations, that other reputable outdoor websites are willing to link to it and build the page’s authority, then I’d have a very real opportunity to rank high in organic search for these search terms (meaning, my page will come up first when someone searches for hiking backpacks).
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