A free user receives an email to the mail once the first time they are added to the account.
Free users are users who are not counted on the payment page (they do not need to be paid for) and can not see any of the interface pages except their profile and authorized lead cards and the customer. You can rename a free user (name). The default name is the email address.
A free user can be paid. To do this, go to the "Settings" - "Users" and open the user's card. Then select the desired group.