Migrating vBulletin question

[hotdogcooker]

Hi all,
I wish I just knew how everything worked with vBulletin from the start but, in the first place I did not understand how you start a vBulletin forum in the first place (which kind of server to use).

So I learned that you can start with shared web hosting, until the forum is big enough that you need a VPS.

But my question now is, how do you migrate a vBulletin forum while people are posting stuff hourly?.

Also, how do you know know for sure when a forum can't last any longer on a Shared Web Host?.

Thanks in advance for any tips and my apologies for not already knowing these things.