The public Google pagerank has in the past been updated from 1 to 5 times a year. In 2012 there were four updates (Feb. 7, May 2, Aug. 2, Nov. 7). There is no way of predicting when the next update will be.
The pagerank displayed by the Google toolbar is not the "real" pagerank - it is only an approximation. The "real" pagerank (used by Google to decide where to list your site on the search result page) is not disclosed to the public.
Even pages with no page rank show up in search results. You can speed up the time Google will discover new pages by using Google Webmasters tools - in particular by submitting an XML sitemap.
New pages seem to get some "Google love" when they're published (i.e. they are ranked higher than can be expected). This is presumably a countermeasure to the "early voter problem" that may bias SERP rankings. If this early "Google love" does not results in popularity (e.g. inbound links, click-throughs), the page will tank as it ages.