As many as you'd like!
Mapware pricing is based on data processing and storage, not number of users, so you can add an unlimited number of users to your Team. Remember you can then set permissions for each user you add to a Team.
To learn more about User Accounts and Teams, click HERE.
NOTE: Billing is associated to a team, meaning that everyone who is added to your team will have access to that billing tier. However, if you create a separate team, that team will have separate billing details attached. This can be useful if you are managing multiple clients.