Current guess on 'first chapter' of fic I'm working on right now.
I put "first chapter" in quotation marks because there ended up being a natural chapter-break at the 9,128-word mark. (It would have cut from a character violently vomiting to a bland domestic scene, and from there to the prior character recapping the next few days. ...Sometimes the fic just taps you on the shoulder and says "I'm ready to end the chapter now".)
The PLANNED first-chapter equivalent, however, is going to cover a chunk of backstory necessary to set up the general fic, so I'm guessing 25,000 words for that. In the meantime, I think I'm going to be labeling the next few chapters "Child Without A Name, Part [X]".
Of course, it has to actually get up to two finished chapters before I can really start making any silly noises about what I'll name the next few chapters...