RentACoder question.

Hey.
Ive just placed my first bid on RentACoder (yeah yeah I know, lots of work and little money..but this poor student needs the extra income). I was just wondering if anyone with previous experience of this could shed some light on a question I have...

What happens if I for some reason is unable to complete the project in question? (For example, if I in the beginning of the project realise that it is all way out of my league). I cant find any information on the site about it. Do I just notify the "buyer" of this and he just begins searching for a new coder? I just want to be 100% certain what I am getting myself into before I start.