It depends. If your goal is to have a higher income, only some graduate programs tend to produce this such as an obtaining an MBA or going to medical school to become a doctor.
I have no idea . It depends on your interest , that is your first choice ; Second , consider your plan ;
wow contradiction here? first you said its completely dependant on his interest, then you said first he has to complete the studies first. What kind of messed up logic is that?