Backup Exec 2014 Server ESO

Hi,

We have 12 branches with 12 file servers. We would like to manage backup for all the branches from head office .

1. Do i need to purchase 12 Backup Exec server licenses along with 1x enterprise server option?

2 Can we install Backup Exec server on file server as we have sufficient space.

Note as we are running on budget, we are not planning to have another physical server on each site. Will you please suggest what could be the best solution.

Thank you