what determines a "billable account"

Hi all. Quick question.

I have the Cypher plan and I was wondering what equates a Billable account. Does this mean it is a "user" with it's own seperate FTP? Or does it mean, an account that is actually a paying account?

For instance, I have my service domain, but then I have 2 other sites I want to transfer to my cypher plan, but I obviously won't be charging myself. If I signed each domain up as with one of my plans and made them "without billing", would this stil take away from my 15 allowable accounts?

Or, I could just add multiple domains to my service domain? Just wondering what the best road is to take. If I add multiple domains, would these all be accessed under the same FTP? Or could I still have seperate FTP logins for each site

If anyone has any light to spread on this matter, I would appreciate it

thank you in advance,
-nick

Easy one.

If they have their own control panel then its a billable account.

If you need seperate ftp accounts then set this up as a unix plan as windows does not have sub-ftp support.