Office365 small business and adding single Office 2013 desktop

Hello

I have office365 small business (p1) and just one user that would like to have the desktop office apps by subscription.
Whats the best way of doing this ?

There used to be an option to add an incremental number of desktop office apps (without upgrading everyone).
Is that possible under Office 365 Small Business Pro ?
Or is it possible just for them to use Office365 home or ProPlus - or does the whole account need to be upgraded to Small Business Pro (at some cost - when its just one user we are talking about).

Thanks