Cash Reserves - 6 months of monthly expenses?

[Alex Witte]

Hello all!

I know it is a "to each their own" kind of topic, but I wanted to get a gut check on what others are doing for cash reserves based on their portfolio. 

My portfolio is small. I have 5 units and I am in the process of my first flip. My primary business strategy is buy & holds. 

I am working on managing my risk. I like flips, but they take up a huge amount of cash. I think I have $40k into this one(which some of you flippers are thinking HA THAT'S NOTHING! lol)

What do some of you use as a guideline for cash reserves?

6 months x total monthly expenses

Total Monthly Expenses = vacancy, debt service, 10% of GSI for repairs, Property management, and Insurance

Or do you only do debt service x 6 months? 

Do some of you simply just say to yourselves, "I will keep $5000 per property as cash reserves"?

Thanks in advance for any replies!