It’s like putting money in a coffee can and burying it in the backyard.

I'm in escrow on a property with awnings attached to the backyards of each unit of a fourplex.

Up until a decade or so, no-one cared really about minerals since oil companies were not going to put a rig in the back yard of a home in the middle of a city. 

Play in your backyard then branch out. 

Collectibles (think baseball cards and stamps), life insurance policies, any investment with a prohibited party which is you, your spouse, your children and their spouses and your parents. 

However, the property has a sizable backyard and a side yard.

As others have mentioned, I like investing in my own backyard (figuratively and literally by adding a second unit).  

Designed it specifically for Airbnb - added a lot of amenities to backyard

The opportunities you seek are right in your backyard.

. :-) I'm trying to strategize beyond "Backyard" investing, in the line of thinking that it could be a better option/strategy.