We are in a situation unprecedented in modern times that requires temporary flexibility beyond standard law. 

There is a detached two car garage with an efficiency apartment that has been vacant for years and will need a full gut.

It's really nice because it has a modern layout and your tenants can setup autopay. 

My main goal is to buy and hold & to build these ADU's the easiest and fastest way possible with less drama....Have a couple of questions:1- Is it easier and faster to work on attached or detached garages?

The property is a single family home (3b 1.5b) no garage.

Crime is only an issue in the inner city - which of course is 1000% of the cheap deals, the majority of Milwaukee is at least fine.New style duplexes (1960s) are generally easier and less expensive to work on; the basement is made of cinderblock, you have drain tile and a sump pump, modern style electrical and plumbing systems, forced air with AC instead of radiant boiler heat, more closet space and bigger bedrooms/open-er concept.

I prefer NOT to rent my garage space to tenants on site; it doesn't diversify my risk enough, I feel. 

Which is a 1950 Cape Cod 4 bed 2 bath, single detached garage. 

In my area, people do appreciate seeing a "modern" refrigerator. 

The only "unsafe" experience I had was related to a homeless person blocking my garage (this was back in 2016).