What is the most conservative methods for tapping into the equity and slowly building my property portfolio.

In fact  such homes are often of superior quality because they are built in climate controlled indoor plants rather than lots of inclement weather. 

The quality of his tenants also keeps him on his toes.

It's simple: He complies with the payment dates and method detailed in the lease or you move to evict him.

Right now the rating for Z is "neutral" and Rdfn as "sell".Most of realtors I talk to feel the discount brokerage concept can sacrifices service quality.

My goal is to use the BRRRR method and have at least 11 more rental units (either SF or small multi-family).

Its important to note that the rent from the 3 units is added to your income to qualify (less advantageous calc method)  and is not used to offset the mortgage (more advantageous calculation).Also you have two current loans outstanding VA loans that have 67% of your 667k limit tied up.

One of our quality standards for renters is that they are non-smoking.

Research the BRRR method as much as you can and build that wealth portfolio. 

If you choose to buy Turnkey, there a few quality companies that are trying to do business the right way, but there are few with long histories to build reputations.