I would think that you both could use the same computer. Use the same account for both of you, or create separate accounts (e-mail, user name, password) for each. Your choice, but I would go for separate accounts, myself.
So, with separate accounts, you could be on with your account, then log off. Later, he could log in with his account.
Separate accounts would enable each of you to have your own AdSense, Amazon accounts, etc.