You can have up to 6 people co-managing your artist page at one time, including yourself. That means you can invite up to 5 additional collaborators.
It's worth knowing that inviting someone to co-manage your page also invites them to become an Artist-Member of the Subvert Co-op. Co-op membership is required to co-manage a page - when they accept the invite, they're accepting both. It's a good way to bring your bandmates and managers into the co-op without them having to apply separately.
This limit applies to the total number of active collaborators. Pending invites that haven't been accepted yet count toward the limit.
If you need to make room for a new collaborator, you can remove an existing one from the Collaborators section of your dashboard.