How is the Zakat calculated for an apartment bought with the intention of investment and rental, and does it include the capital or only the rent, and what if it is impossible to find a tenant for more than a month?

Zakat is obligatory on an apartment if you firmly intend it for trade. It is appraised every lunar year, and a quarter of one-tenth of its value is to be given as Zakat. As for the rent of the apartment, Zakat is not obligatory on it unless it reaches the nisab and a year has passed over it. It can be combined with other funds to reach the nisab. Zakat becomes obligatory on each installment of it when its year is completed, or a fixed day in the year can be set for giving the Zakat on all the money.