A back office and several sites

[eluser]Unknown[/eluser]
Hi.

I'm doing a manager for several sites but I don't know how to store them.

I have the front and the back office in my "application" folder.

I want to centralize every sites like that :
- /application
- /sites
-- /site_1
--- /css
--- /images
--- index.php

Is it a good idea or I have to put the "sites" folder in "application" or other ?

Thank you in advance.