I am 18 years old and need some cash to study for machanical engineering,two worlds apart, and I am really good at drawing... the problem being that I have never done any course or subject on art, so I am clueless. Thanks for the help...

Try e-Bay

I would first research ways to prevent your work from being copied or stolen. Things like putting up low res thumbnails. Or using watermarks.

There are lots of sites that give info on using e-Bay. But it's a simple way to place your artwork online for people looking for art.

Also deviantart.com, totally dedicated to art.