You would do that if the sub portals are all for different clients. However if you are just trying to create different secure areas for different groups of people belonging to the same client, e.g. business groups on an intranet, then there is probably no pressing need to create sub portals. You will instead just apply permssions to the different areas, pages and modules.

The one big task that one seldom sees discussed is; how to convert the needs and requirements of your client and their audience into an appropriate and flexible set of roles. Everyone needs to do this and get it right at the very start, so plan on spending some time on that.

You can create a master portal and clone the whole thing. If your work procedures are tight, and you maintain the master carefully and with good record-keeping, then you'll save yourself months of work over time. Then you can pass that efficiency gain on to your clients as your competitive edge.

Rob

P.s. I often advise.. wear a helmet for your first few months... or aim for the gel-rest if you have one.