Rule of thumb cash reserve:

I think this is what you will need:

12 month cash reserve (does not have to be cash, some liquid assets will do). 

That will cover living expenses, all mortgage liabilities, taxes, etc.

For owners of rentals, always have the reserve to handle the worst situation. I have written several times on this.

For example, if all you have is a 27 unit complex and it burns, you will wait at least a few months to get the insurance money. In the meanwhile you still have to pay.

I had a property that burns, that took me a year to fully restore earnings and half a year before getting the insurance to pay. I had to use incomes from other properties to fill the hole of rebuild costs.