Because of this, they're purchasing their own supplies/materials with very minimal labor expenses.

Gotta get you a good PMS to manage effectively.

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.

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.  

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.

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

A virtual assistant could easily help with the day to day listing management, guest communication, and other virtual tasks.

This is why you always use a property manager.2.