Part of getting a PPL is learning the rules:
1 - to carry fare paying passengers you need a minimum of CPL
2 - to carry fare paying passengers you need to be operating on an AOC
3 - to carry freight you need a CPL but not nescessarily an AOC
4 - to carry work mates in the company aeroplane, a PPL will do (but there are some requirements). The company can pick up the tab.
5 - to carry your friends in your aeroplane each can contribute and equal share to the cost of the flight - UP TO a max of 6 pax