And you are wondering if you should spend lets say $125,000 on a house you have never seen ? 

However if you are self managing, that is work. 

But even being a Landlord and outsourcing that staffing via Property Management still requires someone to manage the managers. 

  (700+ properties yielding 600K is less than 1K/property before expenses)   Lastly,  many property management companies refuse to manage S8 housing for the above reasons so good luck. 

I've managed up to 400 rentals and never offered a concession.

However, consider STR seasonality, local regulations, and management demands, and ensure your equity loan and new primary residence costs fit comfortably within your budget.

I have house hacked both properties while updating them.

You can open a Self-Directed IRA and use the IRA funds to buy a house using a Non-recourse loan. 

Metron and Southern Water Management are two that we've been talking to.

A great way to get started if you currently have a W2 job is to buy a house hack like a duplex or a fourplex where you can move into one of the units and continue to rent/manage the other units.