People do not always stick with their first thought process during times of turmoil 

Isn't diversification a basic principle of building and keeping wealth?

I guess I have been hesitant to bombard people with the same message three times.

Next time you talk to the renter that's paying late all the time, Maybe mentioned to him or her without getting too involved in their personal life, they should seek out a temporary job a few hours, a couple of days a week until they build up enough to get caught up on the rent, and make a little pool of money to use so they don't get behind again.Some Temporary jobs can be fun, like handing out rubber id bracelets at functions to the participants, or if the person is more blue collar they have jobs for those people too more suited to their tastes. just my 2 cents.

This is an area of a lot of ex-pats and longtime vacation takers, or people that have rentals there.

The catch is that the veteran can't then use their VA loan again until that house is sold or refinanced (so basically you have to go conventional in the future, at least for a while).

That means if you and another veteran apply for a VA mortgage together you can build or buy a property with as many as “six family units (the basic four units plus one unit for each of the two Veterans), and one business unit.”)My Take:I interpret this as possibly a mixed use building with 6 residential units and one business unit like a restaurant or coffee shop down stairs.

This is far from impossible and many people have a lot of success managing their own STR, but it sounds more involved than what you're looking for.

The concerned neighbor requested us to do something to put an end to the endless stream of unsavory people coming and going from that rental, with the main tenant in the middle of all of it.

That's how people get over-leveraged and into trouble.If you want to invest, do it the old-fashioned way: increase earnings, reduce expenses, save, then invest.