We have an existing tenant in our single family home rental property.

I bet your systems are amazing, and you probably save a bunch in economies of scale. 

In terms of commercial real estate events, your best bet will be to find events happening in Manhattan - there really isn't much of a commercial networking scene in other boroughs. 

If it were a single family residence, I would lean toward Central as it would help resale. 

You can reorganize your many LLCs under a Series LLC structure and have a single bank account 

Does it make sense hiring a property manager for a single apartment property?

Most renters prefer to rent a single family home, but most investors prefer a multifamily from a returns stand point.You should probably consider a multifamily if you plan to house hack.  

It's up to the appraiser how much consideration to give to the Income Approach to value versus the Sales Comparison Approach commonly used for single family homes.

I invest in single families all the way to apartments and office buildings

Currently, we do own and live in our single-family home.