Try using Fiverr. https://www.fiverr.com
If your portfolio is good and if you know what people want (for example, there are so many people who are searching for artists that would draw their OCs or themselves as manga/anime characters), then you can earn quite a decent living. It takes a bit of time to build up your customer base, maybe a few months, it depends really, but if you're good at drawing you shouldn't have any concerns.
But for the love of god, don't underprice yourself. People will think your art sucks or that you're using some weird ass shady techniques (like stealing somebody else's art or tracing) to make it and won't wanna buy. Do some research on what other people are charging for similar projects and stick with that. Basically, don't uderprice, don't overprice, stick to the middle. 
