Answer:
Poor people have it. Rich people need it. If you eat it you die. What is it?
Sometimes I fly as fast as the speed of light. Sometime I crawl as slow as a snail. Unknown until I am measured but you will certainly miss me when Iām gone.
I must be broken before you can use me.
I am a protector. I sit on a bridge. One person can see right through me while others wonder what I hide.
The more you work the more I'll eat.You keep me full I'll keep you neat.
No matter how little or how much you use me, you change me every month.