What is the obligatory Zakat on a shared building that is leased, and is Zakat obligatory on an unleased apartment, and is it permissible to give Zakat to relatives or coworkers, or as furnishings for a mosque?

If a building is jointly owned for commercial purposes and for rental exploitation, then there is no zakat on its principal. However, the money obtained from its rent is subject to zakat if it reaches the نصاب (minimum threshold) and a whole year has passed over it. It is permissible to give zakat to poor brothers or colleagues. It is not permissible to spend it on mosque furnishings such as carpets and air conditioners.