if they mastered a career is it necessary for them to still work on career? will they still get paid

Mastering a career means only that they now earn the highest salary for their profession. They still get paid in the same ways that they always have at lower career levels.

After they have reached master level, they don't have to continue to work on their career, as there is no more progress to be made as far as earning promotions and raises. They will continue to earn the small bonus for completing a "work cycle" when they do "work on career," in addition to their normal salary. I find it more beneficial to have them do other things to help ensure a longer life (treadmill, workout, etc.) especially if their salary is high.