As an artist, Casetify can be a nice source of passive income. I've had my Casetify shop for about a year and I've been doing pretty well. All you need to do to open a shop is contact Casetify using a form on this page. You should have some work to show them (since you have to be approved to open a shop). If you don't have a website, you can set up a portfolio on a website like Behance for free. If they like your work they will send you an email with instructions on how to set up your shop by uploading a few designs and later setting up your Paypal info for getting paid.