Scott from Bigger Pockets speaks there regularly. 

Then a regular 1031 exchange can be done with no problem.

I don't enjoy nurturing and closing sellers on a regular basis.

I am a strong proponent of what I refer to as proactive asset protection but its not promoted because its not the revenue generator that other asset protection services yield.

I would also advise that you keep an emergency stash of cash in your regular bank.

They are regularly getting poor valuations compared to the cost to add the ADU.   

From there it's your regular ol' cash on cash return calculations!

Would you still use your friend as your GC and just pay him his regular rate (and would they be happy about the new arrangement)?

I don't know but I have plenty of Canadian and American friends and acquaintances who travel (regularly) to Mexico and the Dominican Republic but I don't actually know anybody who has vacation in Puerto Rico (unless they haven't told me of course).As can be expected, the most profitable form of real estate investment in the region is short-term rentals.

And he knows who's working regularly, who's only off-and-on, who's going through troubles, who needs extra work.