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.
Clearly, there's a lot of demand on Amazon, and if any product is going to sell, it's going to sell well on Amazon. But the goal here is to source the right products that will easily sell at the world's largest online retailer. Generally, products between $10 and $50 sell very well here. Just be sure to do the right market research before jumping on this bandwagon.
Are you good with research and data? Are you an expert in any particular facet of business? If so, this could be a windfall for you. Trust me. I do a lot of this myself. I use my experience and expertise as an entrepreneur to offer clients advice on how to launch their own businesses. I do it all virtually, and I usually charge around $200 an hour for the service.