If you are a digital artist, there are multiple ways to make money online.
Offer your digital art services through the platforms like Upwork, Fiverr, and 99Designs,
Sell your digital art through platforms like Fine Art America, Etsy, etc,
Use your art as a design for various clothing and home items and sell them as print on demand products through eBay, Amazon, etc.
Create digital designs and sell them through markets like Creative Market, Creative Fabrica, etc.
Well, there are unlimited options. But you need to remember a couple of things, one, you need to be very best at what you do, you need to try a lot of things and you need to have patience. If you cannot sell in a week, don't get discouraged, keep on trying.