You can form a holding company and have as many fully owned sub companies. You can use a DBA, LLC, Corp. for each of them.
If your companies will do business with each other then you should check out taxguru.org and specifically Choosing A Fiscal Year for how to do this.
If your companies will do business with each other then you should check out taxguru.org and specifically Choosing A Fiscal Year for how to do this.