Should employees get paid extra money to do these things? Why?

- Work weekends.
Yes. To motivate your employees, you should pay them extra money. If you hadn't paid them for work weekends, they would have felt upset and quality of their work will decrease.
- Take documents home to read in the evening
No, you shouldn't, becouse they might have lose or spoil them.
- stay late to finish a project
Yes. If employer spend extra time for his work, he should get extra money for that.
- make phone calls...
- No. During the journey can happen anything.