I am from northern lower michigan and live and build in texas but I am considering building again there next year .

It really depends on the living situation too.

Both apartments had multiple people living in them who were not on the lease and my property manager failed to do anything.2. 

It likely will not go well because you are way too late on this.If you were a tenant paying rent would you want to just get a letter from the new owner telling you to get out with no prior conversation or warning?

Always happy to discuss the situation on the ground if you want to reach out, as I live, work, and invest here.

a live in flip that leverages your own skills and contacts could be good - it's a lower risk way to get started.

Note that in most jurisdictions, if you rent the primary unit and live in the JADU, the primary now has become rent controlled. 

Personally as someone living in Old City the many developments along Christopher Columbus Blvd, and the capping project along I-95 near present great opportunities in the future for new shops and restaurants.What are your thoughts!

Does anyone have any insight on this area as we currently live in another state.

Even a hands off garage conversion ADU is significantly more costly than $100k.