You mentioned buying a fixer upper with your HELOC and now are talking about a 20% down payment.

In the years that I've represented primarily BUYERS, I find that there has been challenges navigating transactions where the seller is a For-Sale-By-Owner (FSBO) AND inexperienced in handling a real estate transaction.

An agent is ON YOUR SIDE as opposed to the wholesalers and investors you mention who are in it to make as MUCH AS POSSIBLE FOR THEMSELVES!

I’ve mentioned it to people at work and some friends who are moving to the city, but my place is either too far for them, or they prefer their own space.

You mentioned that you've been paying water / sewer for all 4 units. 

I'll echo what Zeke mentioned about interviewing multiple realtors / PM's / Contractors to make sure you can get a good idea of what the area is like, in addition to working with someone you're comfortable with. 

As mentioned, one could run it sec8, for more $, and the sec8 waiting list has been full for 7+ years now.

Building a relationship with tenants is important like others have mentioned.

as other post mentioned, it appears that its personal property and not real property and taking it over like someone would take over a car. 

You mentioned the following: "Take a look at what markets you are planning on starting in and make sure it is a growing market where the appreciation is obvious (emphasis added)."