I wouldn't inform the tenant of this until about a month before (or whatever the minimum length is in your lease) that you won't be re-signing him as to not cause any more tension in the relationship which could result in damaged property or him not paying rent.

To be a legal shear/brace wall the minimum length is 2ft-8in for a 8ft wall (that is the wall segments between door and window openings).

It can be frustrating and lengthy based on the type of loan you go with. 

Officially converting a single family to Multi Unit is a lengthy process where you might end up with nothing.I would call zoning and get more information on the area. look at you lot size etc.... 

We've fired a few property managers for lengthy turns over repeated time frames. 

It turns out this was her childhood home which she had recently inherited and she just didn't want to deal with any sort of lengthy sales process on the open market.Am I competing with the zillows of the world?

The seller is giving me a hard time about the length. I

Start an eviction process as soon as the tenant default, best case scenario you work out a deal and drop the case, worst case you move forward with the eviction and you didn't lose precious time trying to make things work (guessing you're in a C-D areas of Detroit, tenants are well aware of the process and like to play the watch to stay in the house for free as long as possible), navigating the courts since covid is a lengthy process so the sooner you start the better. 

Does anyone have or know where I can find a detailed/lengthy checklist for purchasing property from A to Z?

Few investors I feel hold sfh for any lengthy period of time of 10 yrs or longer.