To preserve this friendship and deal you may need to let go of the commission on this deal.

Satisfying the cash/income needs is a must but of course if they're able to preserve and accumulate wealth all the better.  

I would nail down a city that you want to invest in and start developing your core 4.

I think Allen nailed it. 

That said, @Lorien Rollins has hers nailed down with minimal time input/wk 

@Chris Seveney hits the nail on the head, you don't need concrete "legal proof" to provide to a realtor when submitting such offers.

Now for all NON-NAR entities, MLS's, they'd be suicidal idiot's to continue the practice that NAR just lost suit at, because it's a slam-dunk suit to nail them for exact same thing given the now established precedent.     

While some of us want to preserve it within the family, others, including my late grandfather's wishes expressed through my grandmother, are inclined to sell if we can't make it financially viable.The house itself is a 1 bedroom, 1 bathroom dwelling.

If yes, then aim for a specific avatar and nail it! 

You would want to work closely with your CPA or a good 1031 company to nail down the timing of it all.