I put some money with a brother, who is buying properties (houses) to rent them, every year the brother pays Zakaat on the profit including mine and add the remaining profit to my capital with him and he tells me the amount of my new capital.
My question is because my money is invested in these houses but I do not owe a house and if I want my money back he will give it to me as money. Is it enough the Zakaat paid on the profit or in my case I have to pay on the capital which is still invested in these properties as well.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If these properties were bought with the intention of renting and benefiting from their profit, then there is no Zakat on the capital money with which you bought them. The Zakat has to be paid on the money obtained from rent if it reaches the minimum amount liable for Zakat, which is the equivalent of 85 grams of gold, by itself or with other money added to it, or gold, or silver, and a whole lunar year elapses on it. So if the rent money reaches the minimum amount liable for Zakat and a complete lunar year elapses on it, then Zakat has to be paid on it at the rate of 2.5%.

Finally, it should be noted that the Zakat on rent money according to the above conditions is obligatory on the money of each one of you, i.e. you are obliged to pay Zakat on your share in rent money if it reaches the minimum amount liable for Zakat and when a complete lunar year elapses on it, and not on the total share of both of you.

However, if these properties were bought with the purpose of selling and getting a benefit from them then they are considered as tradable items. In this case, Zakat has to be paid on the value of these properties and on the benefit thereof when a complete year elapses on the capital money with which these properties were bought.

Allaah knows best.