Hi, I've created a a video that explains about seting up child portals.. It's here -

But what you need to look at is this module From inventua - Called Shadow Content. It's like the mirror content function where you can change one thing and it's reflected anywhere, but in this instance, is like a super user content manager - so you can change at one portal, but not the other, perfect for franchises, companies and associations that one some content managed by *head office*.

To create this perfect environment you need to plan your master site first - get the pages, content and structure right.  Then go to Host/Portals and EXPORT that portal and give it a name - MasterTemplates or something familiar.

Then, upon creating the child/parent portals, you assign that template at that point, or, use the Portal.template - it has a nice plain installation with none of those extra pages and files you need to delete if you use the standard dotnetnuke one, and you use the wizard after it's created and replace the content, skin and containers through the site in the process.

Hope this helps you.

Nina Meiers