advice on hiring a nanny, please.

Hello, my husband and I are looking for a full-time or committed partial-fulltime nanny. I need advice on what the standard is. Does caretaking include picking up after the kids (not cleaning per se), preparing their food, taking them out to activities? What is the salary range? I`ve heard a gamut. How much more for English-speaking? We have 4 and 2 yr old daughters and we live 30 min. outside Prague right on a commuter rail. My husband is Czech, I do not speak Czech although I am trying to learn.