Apple iTunes ideas

I think iTunes should make it so accounts can have two different passwords, for example, my brother and I share an iTunes account. What bothers me is that I only know the password and he is always wanting apps, so I have to put my password in. I would tell him the password but, what happens when he tries to buy something and I wouldn't know? What I'm trying to say is, iTunes should let you have two passwords for one account, one password lets you get stuff that is free, while the other one lets you spend money.