As an independent consultant/freelancer, do I have to "train" someone on the work I'm doing?

I’m an odd impasse regarding a company I’m freelancing at. I do some custom webpages for them. Things are not going well. I expect them to have me train someone to do the pages I create. I’m simply not willing to do that. Why? Well, first of all, distilling years of design to a “newbie” will be very difficult. In addition, I just feel like it’s just simply beyond the scope of what I do. I liken it to having a plumber work on your pipes, and then before he leaves, you have him teach you his many years worth of experience. Obviously, that simply wouldn’t happen. So, as freelancer, how do I explain this? Can it result in some form of litigation? I know I can expect to be kicked on the curb for this, but I feel this is just not the role I was hired to do. Looking forward to any and all advice!