Illustration careers need a strong and unique style to gain attention and generate interest. Due to greater market competition, simply promoting one's own artwork on social media, isn't going to be enough to secure more work.
'Print on demand' has it's pros and cons but it is one way to market art with less risk. It involves working with a supplier to customize a particular product using your own design input, then selling them on a per-order basis. For a fraction of the cost, you can sell creatives online, thus eliminating the risk of investing in artwork that aren't selling.