Answer:
If a man carries my burden they will get crushed to death. Though not rich I leave silver in my track.
I produce wool and spit a lot
The person who makes it sells it. The person who buys it never uses it. The person who uses it never sees it. What is it?
You throw me out when you use me and take me in when you are done.
I am what one cannot keep, two cannot hold, and three cannot destroy. What am I?
A little house full of meat, no door to go in and eat.