If a collaborator has been added to your account, they will not need to purchase an additional subscription. Only one subscription is required for each account, and multiple users can access the account with the same subscription.
You can simply add your collaborator as a user on your account, and they will be able to access all of the features and benefits without needing to purchase their own subscription.
If you have any trouble adding your collaborator to your account, you can contact our support team for assistance.