How is zakat calculated on money deposited for investment in medical equipment and real estate, and is the zakat due on the quarterly profits or on the original capital?

The money must be purified (by paying zakat) if it reaches the nisab by itself or by combining it with other cash or trade goods. This is done at the end of every Hijri year. The profits generated from this money follow the principal and are zakat-eligible with it, except for what was spent before the completion of the year, which is not subject to zakat. It is permissible to pay zakat from the profits, or from the principal, or from other money owned by the zakat payer, or from money he borrows. The objective is to fulfill the obligatory zakat.