How much would you suggest having in the bank after the deal goes through and I have paid the down payment and closing costs?

The best way to get those two close is by inspecting regularly. 

I look back and I actually came pretty close to achieving it!

It's close to the freeways and medical center.

Raise one tenant up close to market and if they leave then rehab that apartment. 

Is it common for a house flipper to pay a buyer's closing costs?

I you are switching to doing BRRR, then I think staying close to home makes the most sense so you can stay in control of the process. 

I just ( 5 minutes ago) closed on a SF for all in 65k, with 1300 Sec 8 .great numbers a bit more then 10k NET income so about 15%. 

Before considering buying the unit you likely want an inspection of A/C units, roof, parking lot and everything else and try to negotiate a price reduction or credit from seller at closing to repair or replace the items.

@Manny Vasquez came as close as you can come to a perfect post on how to get started!