Is a working wife obligated to contribute to household expenses, and what is the mandatory percentage of contribution if her husband allows her to work?

It is obligatory for both spouses to cohabit equitably and to fulfill their religious rights, which include the husband's financial support of his wife. The wife is not obligated to spend on herself or her home unless it is a voluntary act. Whatever the wife earns from her work is her exclusive right, unless the husband stipulates a portion of her money in exchange for his permission for her to work. If he does not stipulate anything, he has no right to her money, but if he does stipulate, then he has what he stipulated by mutual agreement between them.