Live in one unit - It's a great strategy when using a bank for financing as the down payment and interest rates are more favorable to owner occupants.  

FHA 203k wont work unless youre going to live in the property as your primary.

This one came from Massachusetts, a state where the eviction laws are not in the landlord's favor.

Your investment property - This you could do a 1031 exchange on and buy another property you intend to use for investment. 

I got the property off-market for $250k from a trusted family friend.

The property is located in a prime growing area in northern Alabama.

Would any new ADU sq ft add $450 / sq ft to the property value OR would it be at a discount because it is an ADU?

@Cole Starin sometimes it makes sense to sell the WORST property in your portfolio.Another option is why do a LOC on the duplex, when you could just do a $100k cashout refi to pay off all your debt AND keep the property?

Your property management company can help once you own the property but up until then you need someone good on your side!!! 

In our still relatively limited experience, seller financiers are usually looking to get a higher asking price in exchange for the favor of the private loan.