Please tell me the meaning and answer (brain teaser). How can you make money from monkeys?

1. How to make money with monkeys? Remove k

2. What dog never barks? Hot Dog

3. What goes up but never comes down? age

4. What has a head but no brain? A nail

What is the end of the world (what is the end of the world d?

6. What works but never disappears? water