语法有点错误,主要是词性没有搞清楚。应改为Becoming a leader or a manager is an object of ordinary Staffs, for they may get more money then.
To become a leader or a manager is an ordinary worker's target,for he or she can make more money if he or she realizes his or her target.
become是动词,不能直接作主语的。
后面也不能用because,这个词是用来引导原因状语从句的,表示必然的因果关系。
Becoming a leader or a supervisor is the ovjectives/goals of laborial staff. In that case, they will get more money.
Becoming a leader or a supervisor is the objective of ordinary staffs, in which case, they could get more money.