Does anyone know, generally? I thought 3 months, to 5 at most. But my friends site has been up since March, and he's linked by pr3's I think. They updated google and he still doesn't have a PR. Very strange.
They update it every 3-4 months like MGS said. You should try to get as many sites to link to you as possible, no matter what their ranking when you are first starting to build. As you get bigger, you wanna aim for PR7-8. That will get you the good rank