When is Zakat due on a salary received in installments? Does the amount loaned or overdue count towards the nisab? Is Zakat due on money accumulated to buy a house?

Zakat is obligatory on salary and borrowed money when its repayment is hoped for. It is not permissible to deposit money in usurious banks except out of extreme necessity, with the money being withdrawn immediately upon its transfer. The usurious interest collected must be disposed of by spending it on the welfare of Muslims.