Also, although we like the idea of diversification, we understand that buying a single rental property is itself a highly concentrated investment.

It maximizes your potential for income flow while letting you dabble in real estate.It is a great benefit that you are prepared to work on do-it-yourself projects and concentrate on little improvements.

I'd concentrate on more advertising and then selling people on the benefits of living there once they arrive.

Need to concentrate on stuff here first.My main questions are how on Earth would I target a group of people that are into buying investment properties in Mexico?

This concentrates the equity so it will be easier to access when you need it.If you want a true picture of what borrowing does to your return you have to look at the Internal Rate of Return.  

Try to concentrate on your city.

I concentrate on flips.

Im located in Phx,Az and its common here to still see empty dirt land in prime areas of city, as an example, my father who knows next to nothing about real estate purchased a 7k sqft gated dirt land  in the city 3yrs ...

Why aren't you concentrating your investments there?

And funny enough, Arizona state apparently have the highest ranked online Master Arch program, and they have a concentration in focusing on sustainable development concepts, which seem to align with my interest so I will be looking into that.