There are a couple of things you can do depending on if it's a webcomic or an actual print comic.
If it's print you can either submit to a publisher or self publish/market it. Submitting sounds the easiest but understand that marvel and DC to not except submissions unless you're already somebody famous. Image and dark horse do as well as a few other smaller but well known publishers but they usually want to see 5 finished pages of art, a synopsis and a solid creative team, if not a finished book. Also keep in mind that they get a lot of submissions a year and (from experiance) it's best to pay your artist or it will never get done and I'd say at least 15-20 dollars a page plus more for inking.
If you try self publishing expect 2000 bucks to print 1000 copies if it's black and white or somewhere between 3000 and 4000 if the book is colored. Most people with a steady job can get a comic self published but you'll have to do the marketing, which means getting into shops, if they like it, or comic magazines.
If it's just a webcomic then build a good website, get yourself some links and don't expect to make any money unless you get a lot of repeat hits or if people like the stuff you make to sell, which if you're talking shirts and hats will usually cost between 10-20 per item to make and ship.
It sounds like a lot whichever way but all are doable. Good luck.
