No, you wouldn't have to pay for them twice, Gonzalo.
Business Class is an upgrade for a single Trello team, so you will only pay for members of that upgraded team. Any other free teams won't have any charges associated with them. This is also why that free team won't have access to your Business Class team's features either.
I hope that helps explain!
If you had to thrive a new habit during a lockdown, what would it be? Trello
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