How many public IP addresses needed.

Hello - were going to getting a new ISP and one of the questions they are asking is how many public IP addresses we need.   We previously had our internet access provided by another facility so that was out of our hands.   So my question - how many should we request.   Some of the things we would like to be able to do are:    VPN access, Outlook Web Access, other???    What other things would I need a public IP for....
Thanks