The subscription belongs to the workspace, and the workspace owner manages it. People on your staff (admins and members) are included in it at no extra cost.
Anyone you invite to a single budget, as an editor, section editor or viewer, signs in with their own free login and never needs a subscription. Neither does someone opening a view link.
If you work freelance for several companies, each company's workspace pays for its own staff; you do not need a subscription of your own to work in theirs.
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