I'm looking at a place like 2.5 blocks from it.

I had a flat concrete slab (shaded) where I put it.

Concrete work is expensive.

Look for cross or blocking on the joists for earthquake and general stability. 

Detroit is a block by block city.

We eventually found the perfect property that was located 1 block from the street car.

@Chris Seveney hits the nail on the head, you don't need concrete "legal proof" to provide to a realtor when submitting such offers.

It only takes 2-3 nice buildings on a block to make an impact. 

About classes Detroit is a street by street city not necessarily by class you have class B and a block away is a war zone so you do need boots on the ground for sure DM me or Travis and I give you some guidance but going solo is a little difficult partnering up would be a little easier and less risk but again up to you. 

And then the solution was to block my unit off as owner-booked, or to “resign the listing.”