I've already invested in a duplex in NJ (I'm renting it to two families and managing it) and a single family in MI (living in it).

We obliged.

I use Ziprent property management to find new tenants.

Take a look at some trade accounts and a line at the Big Blue and Big Orange if you are going to self manage.  

You're looking for increased cash flow, so managing more doors and/or strategically utilizing leverage can make a certain sense there...but as you mention financing costs aren't as rosy as they were 2-3 years ago. 

The seller will warrant good title "excepting out" or not giving warranty as to a specific lien requiring the buyer to accept the obligation to clear that lien.

I'm structured and want to pursue something in real estate or money management.

Hence, suggesting a sub to sale to a seller is NOT encouraging him to violate and law or any contractural obligation. 

They may feel a sense of entitlement, and they may not even be good renters.Unless this is some unique situation like a ranch that requires special skills to maintain the property, I recommend you remove the caretaker, spruce the place up, and put it on the market at market rates.I also recommend you look for a professional property manager that can help you navigate this immediately.

how will they manage the property?