• Payments via the Upgrade button apparently add user capacity to a specific user's account, distributed among whatever wikis they own, and not for a specific wiki.
• Next, if we want to transfer ownership of a wiki to a new owner, the new owner doesn't take over either the user capacity or billing for this existing wiki.
• I'm assuming that the new owner could then pay for the appropriate capacity, but is anything lost in the interim? For example, if a bunch of permissions have been granted to initial users or groups, do those get deleted when the wiki gets transferred to a new, initially unpaid, account?
• The previous owner will have paid for capacity that's no longer applicable to the existing site.

So this suggests not creating sites for clients using an existing account, but instead setting up a dummy owner account which will be handed over to the eventual owner, along with the capacity so far paid for (and at that time change its email address and billing info).

But that in turn runs into the problem that one can only log in to one zoho account at a time (at least, one per different web browser), making it awkward to easily jump from one site to another, to refer to private reference information and so on.

Maybe that problem can be solved by adding the same "developer admin" account to each site, which will be the primary way to log in for the tasks of the initial developer.

As previously noted, there seem to be yet further entanglements relating to which account (or some other account) should own the group definitions to be used for setting up permissions. Perhaps if a "dummy owner" account is necessary, it could also own the groups. But I'm not sure.

Anyhow, I hope you see the problem -- is there any advice on how best to proceed on this?