Don't take the advice of if you cant do it in your backyard you cant do it farther way. 

My wife and I want to build a portfolio of buy-and-hold rental properties.We've spent about a year looking for a viable strategy in our own backyard and are almost convinced that we'll have to "trade up" to investing locally in 5-10 years after an out-of-state portfolio has been seasoned a bit.

If you figure out a cost-effective way to put ADUs in your backyard, let me know!

May I ask why you haven't considered your backyard, Cincinnati?

As many of you may know, Governor Newsom signed a series of bills that made it a whole lot easier for homeowners to build ADUs in their backyard.

Also the small house behind it with maybe a 1/4 acre small backyard 200 Sq ft  front 50 sq ft. 

I have some experience with this, but in illinois.I once bought a property that had a smaller house in the backyard, commonly referred to as a coach house, that was called a legal non-conforming structure.

I have a property in Dundalk and my tenant got a $2,000 fine because my tenants left the lid off the trash can and also have debris in the back yard.

Certain structures are not well suited to being brought up to code, which is why there's a lot of companies right now building modular ADUs that just get dropped into your backyard ready to hook up to utilities.  

Baseball bats?