Most mod creators don't work for money. Natural Selection, The Specialists, SI, SC, you name it, were made for the mod community in mind and not for money. However, Counter-Strike started off as a mod without money in mind as well, and was purchased by VALVe.
What I'm trying to say is that mod teams don't work for money, but if your mod is of excellent quality (ie CS quality) and is very popular, it may be considered for purchase by a publisher/dev such as VALVe.