Areas that have been good 30 or 50 years ago are still good today.One wildcard though.The city of MKE has initiated a projected called GrowMilwaukee, which is based on the majors vision to increase population (for fiscal reasons, more people per square mile) and they have identified the lack of midrise mixed use districts - they call it the "missing middle".

Often, people like me surf several different jobs/careers, only to find themselves in their thirties without a vocation--something they can find truly fulfilling as well as profitable.

Does anyone know of any people who have successfully navigated building an ADU on their property locally? 

People will tell you that you can do all sorts of things with a property, but they may or may not be correct.

Again, the BiggerPockets store has some books for this or you can learn by watching podcasts, reading blogs, and interacting on the forum.

There’s a few people dabbling with STR property management but nothing that would make a difference.

But with enough work and connecting with the right people you can make it happen.

It can work, but those deals are best done by people with the money who can leverage that fact against the deal to pay more.

I know that in single families in Cleveland Heights people have put in basement bedrooms with an egress window and they were on formal plans that were submitted to the city and approved. 

On the other hand, you can make money in any area, even areas with no growth as there are still people that live there, even if the population is declining.