Questions on serving same code base to multiple sites

[eluser]Freewolf[/eluser]
Greetings All,

I am getting into CI for the first time.

We have chosen to use it for the redesign of our sites.
We have 4 sites for a college that essentially each site will be very very similiar.
Site layout, architecture and hierarchy will all be the same.
Page content and look and feel of each site will be different.

So I am thinking we can have one code base that will serve up pages based on which URL the user is coming from.

So I am guessing having the system folder at the same level as the www directory.
having 4 www directories all accessing the same system folder.

What are the things I am going to have to look out for and program for.
Just looking for the ideas of what I need to be on the watch out for since we are in the research and planning stage.

Blessed Be

Phillip