As salamu alaykum I own a house but I don't live in it. I am renting it out for $1600 per month. Out of that only $300.00 is left each month (that is after paying mortgage and taxes). So how do I pay my zakat on this investment?

All praise be to Allah. The strongest view concerning this issue is that the money received from the rent will be added to the individual’s wealth. If a person has wealth in excess of the nisaab (legal minimum) and he possesses it for an entire year, he must then pay zakat on that wealth. If, for example, he uses that money to support himself and the money does not stay with him for a year’s duration, there is no zakat on that wealth.