I think you are playing in a dangerous situation if you go the hard money route.I also want to help give you realistic expectations.

If he has been doing it his way for almost 50 years there is a good chance he isn’t going to was to hear it frankly.That said, if you play along, even if you can’t use subtle techniques to move things along, you may win his trust and be given some buildings to manage- after which you can slowly change things.Above all else enjoy your time with him.

This will avoid issues down the road if she is flaky and using boyfriend to play the tenant game.

Two years and thousands of research hours later, I know a heck of a lot more and realize that he probably just sent out a mass text to investors he knew which is how you play the game, right?

I presume you would play by the rules.

I'm not from Mass but have been checking on this post out of curiosity since I don't really understand why to limit access to the basement. 

Why would we assume the best case scenario with this type of situation rather than play it by suspicion and keep tabs on the tenant to make sure he does not create a major inconvenience for his neighbors and potentially significant damage to the property?

I was actually just playing with the calculator on BP and came across a land contract deal from Zillow.

He would build then sell the house + lot (it's essentially a loan to him so he has some capital to play with since it appears most of his is currently tied up). - The return has a hefty minimum but can go higher depending on the sale price

I am not sure how much hardball I should play with this.