Sites belong to Organisations
Every Site belongs to one Organisation. An Organisation has a Plan, shared storage and one owner, who pays for it.
This fits how websites are usually run. A business, a club or a client is an Organisation. If you build sites for several clients, give each their own.
Members
An Organisation can have members. Members can do everything to its Sites (code, data, secrets) except archive or delete them. There are no per-Site permissions: an agent acts with its person's role. Members are added by Haume support for now.
Handing over
When a committee changes or a client takes over a site you built: add the new person, make them owner, and the old owner leaves. The Sites don't move and nothing goes offline.
One bill
Every paid Organisation you own goes on one monthly bill.