You know, I supported myself through graduate school doing this very thing. The way I looked at it, I was being paid for my research skills and writing abilities–that was a good thing–and I was also developing them. You can look at it as work for hire, nothing more.
On the other hand, the people I was doing it for were most definitely cheating. If, as a (very underpaid) graduate assistant, I had run into a paper that I knew not to have been written by the student, I would have had to turn it in. And, had I run into one of the papers I’d written, I would have done just that.
Fortunately, I didn’t.
I also thought a lot less of them for doing it (although my most profitable client was a secretive contact from the athletic department, and I guess I couldn’t really fault a hard-working OU linebacker for hiring somebody to do his research paper on Queen Victoria during the playoff season).
I don’t even feel bad about it. (There is some writing for hire that I do feel bad about, and that was writing speeches and op-ed pieces that were delivered/printed under other peoples’ names, and there were a couple of those that made me feel like I ought to make my extra cash doing honest work like sucking peoples cocks.)
Don’t get me wrong, I’m not saying you have to do it. I just don’t think it’s an ethical problem for you. It’s the kid’s ethical problem. And the father’s.
They’ve already demonstrated that they don’t have a problem with it. Sure, the son would probably learn something valuable by doing it himself, but he’s already got the skill he needs here–if you can’t do a quality job, pay somebody who can.