How much reserves should I have on a property?

[Jack Wyatt]

I did my first deal last year. I bought a rooming house. 13 bed 7 baths. It's a lot of work and randomly there are late-night calls but I cash flow around $4000 a month. It's an old house with its share of problems. How much reserve should I put up? House is paid in full but I will be doing a cash-out refinance this month to try and do my second deal (hopefully another rooming house). I hear Brandon T talk about putting up reserves but I never hear him say how much that should be? Any help is appreciated.