I-phone help needed with an issue?

My husband purchased used from a flea market yesterday an i-phone no sims card, no password and yes used...is there anyway we can bypass the password and unlock this so he can put his sims card in there and use it when he purchases a plan? I can't believe he did this, must have been an impulse buy? Too good to be true or something? I don't know but I need some help with this...please. Thanks :-))