With CRM free you’re able to invite as many users to use the system as you want. All users are under the same HubSpot ID (number in the top right) so, depending on the access levels you set, users can see everything in your portal. See all the features here: Free Tools | HubSpot
To add a new user go to Settings → Users & Teams → Create User. Enter in their details. Set their accessibility. Once that’s done they will receive a welcome email prompting them to create their own password.
From there your new user can use their name and email address when communicating with your contacts. You can also assign a HubSpot Owner to contacts if you wanted so you know which contacts belong to whom.
Hope this helps!