Can I have various users using the same account

Is it possible to purchase one CRM user account and have various employees use it? I dont want to purchase an account for each employee, its expensive for our company. Can we buy 1 user account and then have a field that the employee enters their name so that we know who is using the account or who is editing information.

For administrator level activity can we also do that inside of the same user account, using a password? or should an administrator have a separate user account purchased?