I think if you are running as a DBA for the sub companies, then it would be simple. If you were trying to get true financials, so you can track profits and loss, you may want to use different billing software for each.

I guess you can break the reporting down by product type. At the same time, is another 15.95 a month worth not having to spend a couple hours a month to break a single billing software down to multiple companies?

Personally I always think its nice to know which are making money and which are lossing.

Regards
Jarrod