Answer:
I reach for the sky but clutch to the ground. Sometimes I leave but I am always around.
I am often sold by children entrepreneurs in summer time
I don't live within a house nor do I live without. Most will use me when they come in and again when they go out.
Iron roof, glass walls, I burn and burn but never fall. What am I?
I start in little but I end in full you'll find me in half and complete.
No matter how little or how much you use me, you change me every month.