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. 
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.

Tutor students. Many families prefer the flexibility of using an online tutor. Depending on your background, you could be simply helping a child with homework or providing college-level support. You need to have your own computer and high speed internet. Experience required differs among companies. Some require “strong experience,” while others require a specific educational background. However, most companies do require a college degree.

More and more companies and startups especially are embracing remote work—where you use online collaboration and communication tools to do your work from wherever you want. And you don’t have to be a 20-something hotshot designer or coder to reap the benefits of working remotely. Many remote positions are for customer support positions or other customer-facing positions that don’t require specialized skill sets.

It can take time to build up your personal freelance business. Yet, there is more demand than ever for freelancers. So, if you want to kick start making money online through freelancing you can join one of the top freelance networks, such as Flexjobs, SolidGigs, Contena, Upwork, Fiverr, or PeoplePerHour. Sign up, build your profile, upload some samples of your work and start making extra money by doing small freelance jobs.