Answer:
I am often sold by children entrepreneurs in summer time
I go through a door but never go in, and never come out. What am I?
What kind of room has no doors or windows?
Where I am there is no south, west, nor east, and weather is not fit for man or beast. What am I?
You cannot keep me until you have given me. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.