Assalam-o-alaikum
I bought a flat for Rs. 13 lacs out of which I borrowed half money from my relatives.
And I cleared some loan still I have to pay 2.5 lacs
My income from flat is 3500 pm and this ramdhan almost one year is completed
So how much money I have to pay as a zakah for this flat
This flat I purchase so that I can stay there after my marriage
Currently im staying with my brother and mothers
I have to pay zakah on flat cost or else on the income which I made through flat by way of rent.

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, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

There is no Zakah due on the apartment as long as you did not buy it with the intention of selling it and trading in it. Zakah is obligatory only on its profit if it reaches the Nisaab by itself or by other money, gold, silver, or tradable items added to it, provided that one Hijri year has passed since the possession of that Nisaab. If the money reached the Nisaab and one Hijri year passed, deduct the value of the debt you owe your relatives, and if the residue is still not less than the Nisaab, pay 2.5 % of it as Zakah.

However, it should be noted that the Nisaab equals the amount of 85 gm of gold. For further information about Zakah on rented real estates, see Fatwa 85524.