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.
If you already have a website or blog, look for vendors that offer related but noncompeting products and see if they have an affiliate program. Stick to familiar products and brands—they're easier to sell. To promote them, place simple text or graphical ads in appropriate places on your site, include in a blog, discussion forum, or mailing list links to purchase products that you review or recommend or create a dedicated sales page or website to promote a particular product.
Ready to enter the ecommerce fray? Why not sell your own stuff. Of course, along with selling your own stuff on your own website comes a whole slew of both responsibilities and technical configuration and requirements. For starters, you'll need a website and a hosting account. You'll also need a merchant account (sure you can use Stripe or PayPal). Then you'll need to design that site, build a sales funnel, create a lead magnet and do some email marketing.
Mechanical Turk is Amazon's take on micro-jobs. These are small miniscule-jobs that you can do for other people, which they call HITs, or Human Intelligence Tasks. These are super simple tasks that anyone can do. Some examples are listing off some URLs with certain kinds of images for one cent, or recording a few phrases with a microphone for 6 cents.
Since time is the most precious commodity on this earth, invest the time at the front-end so that you can reap the benefits on the back-end. This means putting in a bit of sweat equity and not getting paid today. Rather, you'll get paid somewhere down the road. And you'll continue getting paid whether you keep building that passive income stream or you stop. It's obvious that this is the preferred route, but clearly the road less traveled.
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).