For reasons explained in this question, I am currently looking for a new place of work. I have recently received a verbal offer from a hiring manager and have been told that a written offer will be forthcoming sometime this coming week, for a start date in early-to-mid June. I fully intend to take this offer; however, for personal reasons, I will absolutely need to take two weeks off in the middle of January 2016 (a mere six months after I join). It is unlikely I will have accrued enough days off by then to take that much time off (as I mentioned, I do not yet have a written offer, so I am unsure as to the specifics. However, from what I have heard from friends who work at this company, I will not have enough vacation time by then).
When do I bring this up? Do I bring it up now, before the written offer is sent? That way, I can get an idea of their vacation policies up-front; on the other hand, I don't want to give off the wrong impression by asking about vacation times before I even have a written offer. Do I wait until after I get the offer and try to negotiate the time off then? Or even wait until after I've started?