Rental Unit Question

[Walther Mendez]

Hey Everyone, I am looking at renting out my townhome in February/March 2018. I would like to save about 4 months worth of mortgage payments before I rent it out. It is currently my primary residence and my wife and I plan on buying a second home around that time frame next year. The townhome was built in 2016 so all appliances are new and no major renovations are needed as of now. My mortgage, HOA, Taxes and Insurance come out to $860 a month and the townhomes near me are renting for about $1200 a month. I do plan on managing it on my own for the first year or so. I do plan on saving more than the 4 months of mortgage, but would like to know at what quantity should I begin to use the cashflow to save for another investment. My question to you is how much reserve should I save for my unit? Is there a rule of thumb I can go by? Thank you in advance!