If you have a reserve of $6,000 for one property, your annual cash flow could still be hit hard by a bad tenant, or the combination of a bad tenant and a failed furnace.I'm curious how you manage to spend 4-6 hours per day on real estate.

The bigger issue is you need the ability to manage the entire process. 

I don't count flipping houses part time or owning a couple rentals, but working as a property manager or asset manager for an operator.  

Can't wait to see you grow.If you're planning to invest out-of-state, I recommend reading “Long-Distance Real Estate Investing: How to Buy, Rehab, and Manage Out-of-State Rental Properties” - I found it to be very helpful when I got started investing 2.5 years ago.

True , GC is like a teacher to subcon , but after years of experience , it is the GC that’s hands on , practical and having leverage.my GC guy would kill me if I hired his subcon and giving him 40 dollar per hour , for example , lol.GC and subcon is like manager and employee in tech company lol ….

Current interest rates are going to make it difficult to reinvest into real estate and not come out of pocket more than $1000 annually, per your current situation.I am also assuming you are paying a property manager with your current figures. 

House hacking will also give you some personal "property management" experience.

We own & manage a few Multi-Family properties in NorthWest Brooklyn (Park Slope, PLG-Lefferts, Bushwick) which I've been managing without issue for the last several years myself.

I like STR but the maintenance gets expensive and frustrating to manage or do myself.

Include not only the mortgage payment but also taxes, insurance, property management fees (if applicable), maintenance costs, vacancy allowance, and any planned capital improvements.