Oh, that sounds frustrating. I think that's the kind of thing that would drive me crazy. 
It will really depend on who you work for. On the one hand, you have friends who want you to edit their first ever fantasy novels, on the other, you have publishing houses that know what to expect... Just be smart on your end, cover your bases, have some kind of contract/statement of work/something and it should be fine. Oh, and don't get emotionally invested in making the thing good.
Thanks for the advice. Having a contract would definitely be important.