I find even the most tenant friendly state/county/City in the US heaven for landlords when compared to Spain. 

Try and gauge how much work it might need, get friendly with the seller.

I think there might be a value play here if you are in certain markets and appeal to more environmentally conscious renters.

I was about 32 and I partnered 50/50 with a friend in an all cash deal.

We got a great job, came out whole financially and managed to keep the job site a friendly place to be. 

I am thinking I can just not have the equity backed by an official note (the people who would be investing with me are a close friend and my family so they trust me) and that would be okay, but I am not sure how un-documenting this large sum of cash would mess with FINRA’s regulations...

I'd appreciate advice in how to structure this specific kind of deal:- Current owner is a neighbor/friend, who is 75 and wanting to get out of two duplexes in the near future (4-12 months).  

Amongst friends and living in a community with more personal space, diverse economy, access to travel (roads / airports) and strong local culture (food / entertainment / socialization).

They were very appreciative of the whole process and if they ever have any friends/family in a similar situation they will let me know.

The Section 8 rules are Landlord friendly.