Kids Riddles

Question: What building has the most stories?

Question: Not chest or box is now discussed. Money can be held in it, but just as we test its metal, within it there is rust.

[What is it?]

Question: You can call me a home, but I have no doors.
Someone lives inside me, but leaves when there's no more.

What am I?

Question: What single line can you add to the following statement to make it true?

5+5+5=550

Question: Which comes first, chicken or egg?