They'll need money, food, something to do, clothes, paper, pens/pencil and last but not least drinks.
Explanation:
They'll need this so they can pay the Van Daan's they need something to eat and drink. They need something to do so they can be quiet and not be so bored. Paper and pen to write things. They need these things to live and survive on.
The must be quiet and respect each other. They do not know how long they will be hiding together so they must befriend each other. If not they will begin fighting making their lives all the more miserable in hiding.