Way to Auction Digital Art Online

Hello people! I've known how helpful the people of this subreddit are. I'm not sure if I should ask Art-related advice here. Please let me know if this isn't the right place.

So I'm a full time Medical student(3rd Year) and an Art enthusiast. I learnt about Art Commissions only last year. Its really competitive out there to get a client and after facing multiple rejections and scammers,I find a great client. However,for the long run I felt like this uncertainty really puts me in self doubt. I love drawing so getting to earn a little with it is really Amazing!

I was thinking of making some sort of Passive Income with Art. Is there a way to do so without having to have a Big Online presence? I really battle with time because I can barely find any when there's so much studying to do daily.

The Kind of Art I do- Digital and Traditional- Anime Realism(Portraits)-Traditional Comic Art- Traditional/Digital Tattoo Designs (Minimalistic and detailed)- Digital

My work- https://www.deviantart.com/tigressive

Tattoo Designs- http://imgur.com/a/TfpH68T

THANKYOU to anyone who read all that! If you could point me towards a forum which would have more valuable advice for me,please let me know.

Stay Safe everyone!