There could potentially be an option for the heirs to assume the mortgage when the estate is settled.

Is that an option?

I'm not smart enough to work out the math of which option would be best, or how long it would take for the syndication option to overtake the DST option. 

I did not want to move or sell anytime soon but fear that this option has been taken away from me.

The owner handles the rehab themselves.So, we rarely charge any fees as our owners typically choose one of the 3 options and they are all a win/win for both of us. 

On the other hand, if you have a lower budget, let’s say $100-$150k.

The 2nd part of the question is which option maximizes the true revenue potential of the property ?

The other guy, who bought in the boarded up zone, has no such options.

Working with friends or family is fine, if you think the same and spend the same.

I've purchased two properties personally utilizing seller financing and represented at least a handful of buyers acquire properties with private mortgages over the past five years including friends and family members.