How much for emergencies per door/property in cash reserves?

[Ian McKay]

How much money should you set aside per door / single family property for emergencies such as covering the mortgage due to vacancy? That's my primary concern with brrrr or any property I don't own outright. 20% or less down is great but if my tenant leaves I have to cover the mortgage which could be 2K a month in Northern Virginia. 

[Michell P.]

Depends on the age of the property and what your local vacancy rate is.  How old is your water heater, ac, etc?  [Cost to replace everything / years of service + expected yearly turnover costs) ] / 12 = monthly set aside into a high apr savings (capex).