Start your own website.

There are two kinds of websites – the ones that sell products and the ones that provide information.
If you can think of a good idea for a webstore and invest enough time and energy into marketing it, you might do well.  But keep in mind, you will have to constantly keep at it.  There will be orders to fill and plenty of accounting and inventory work to keep you busy,  provided you have a good product, there’s demand, and you’ve marketed yourself well.  The “If you build it they will come” slogan does not apply to websites.  If no one knows you’re out there, the chances of them accidentally stumbling upon it are virtually nil.  It can also be expensive if you don’t know how to create or operate your website, or how to market it.  You may very likely need to enlist the help of paid professionals.
If the idea of running an online store does not appeal to you, perhaps you’d like to create a website that offers information, rather than products.  It could be that you make brilliant cartoons and think that would get a following, or perhaps you’d like to start up a news blog or maybe even a site for dog owners.  There’s no limit as to what topics you have to choose from, but my advice is to choose something that you love.