There are so many different acceptable citation forms. The three with which I'm most experienced are APA (utilized during my graduate program in social work), Chicago-Turabian (utilized during my graduate and undergraduate programs in history) and MLA, the format most widely used by public high schools in the United States.
While these are the ones I'm most comfortable with, I can adapt to any other, as well. But there are such tedious differences between even those that I'm best experienced with that editing a bibliography, endnotes, and/or footnotes takes significantly longer than anything else. That's why my standard price for citations is per citation as opposed to my normal per word cost. It's a dollar per citation unless special arrangements have been made.
My advice to most non-fiction authors requiring detailed citation is to become confident and well-versed in it themselves. Presumably if you're writing non-fiction you'll pick one format and stick with it. Provided you pay attention, you can become as good at it as an editor. You'll save money and time, because eventually, it becomes second nature. I felt that way about Chicago-Turabian while studying history, and about APA while studying social work. It's when I have to go back and forth between styles that it becomes more tedious!