There are no restrictions from my point of view. It depends on how each person who wants to become an ECA wants to arrange his/her own business. If he/she wants to be an ECA only, then he/she should focus on posting items for sale only. If that affiliate want to get a passive income also from all the other features on SFI, then he/she should focus on all aspects and make daily points, make a team etc. It depends also how much time each ECA has available for SFI.