Is it possible to add additional paid users to a Google apps for business account whilst keeping the existing free users free

Question

Ive got a google apps for business account with free 10 users, ive assigned all of these and would like to add another user.

They no longer offer free google apps accounts so i would have to purchase new users, but do you know if i have to change my existing 10 users (which are currently free) to paid users or can i keep them as free users and just pay for the additional 1 ?

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UPDATE

In response to Pnuts answer Id like to expand on the question :

If I have 3 domains running on the Google Apps Account, do i have to updated users of all the 3 domains to paid or only 1 domain at a time ? ie. if it updated 1 user of 1 domain id have to update all the other users of that domain, but not the users of the other 2 domains

Answer 1

No, it's not possible.

This is because once you have upgraded a Google Apps legacy account to Google Apps for Work or Google Apps Unlimited, you have to pay the licence fee for each account before the trial period ends or all accounts will be freezed.

References
Upgrade to Google Apps for Work - Google Apps Help