need 2 accounts, share all files, but not email/messages

Please let me know if anybody has any ideas on how to do this.

We have a computer which we would like to share with 2 adults (and possibly later some others). We would like 2 separate accounts, in which we can log in separately, and share almost everything:

• files
• documents
• music
• contact list
• calendar and events

However, we don't want to share email or iMessages (ie: text messages which show up on our laptop).

How do we set things up so that we have privacy with email/iMessage, but share all those other files?