Labno, Yes your question was a little confusing but I get what you are trying to ask.
First of all, Please before you venture into your own business and subdivisions, please make sure you Incorporate.
So the answer to your question is: Yes you will have to register all your subdivions in the county registrar. So for example lets say you call your Corporation "Mycorporation LTD" your subdivions automatically become DBA`s to your corporation. So at the county registrar it would be filed as "MycorporationLTD" doing business as mycompany1, 2, 3,4,5
So yes they all have to be registered.
Keep in mind registering your dba`s doesn`t mean you will have a different EIN for every single one of them it basically means all your dba`s will have the same EIN number, but each can have its own checking account and everything else that comes with owning the business.
Let me give you an example of my company.
The parent name of my company is: Hispanic Marketing Strategies Inc.
I have three dba`s:
1. Nuevolution Web Design and Consulting
2. Nuevohost Business Hosting Solutions
3. Cyber-Tech Plus Computer Repair and Service
They all have separate bank accounts, But they all share the same EIN.. This is true until you Incorporate one of your DBA`s (tooo much paper work though)
When I filed at the registrar I had to By law advertise it on the newspaper for two weeks I believe. and I had to file for each DBA...On the same paper I think the difference is like 4 bucks here in CA for each additional DBA.
Web Developer / Owner / Consultant
When starting your own business the need to "know-how" is greater than money!