"Moisture and dirt are entering the basement near the stairwell""Additional support columns/beams lack visible hardward securing them into place"Engineer noted there is no structural component dug below freezing level on any of these supports which would need to be done to get the foundation supports to code"Signs of water penetration noted on the basement walls"Picture showing proximity of nextdoor house"The soil slopes towards the foundation, or is flat, and must be corrected to prevent water from finding its way to the foundation" (This is the side of the house with the failing retention wall in the basement and has extremely limited access) The engineer recommended potentially just paving cement between the houses to seal it and recommended against a french drain as installing it would go below the level of the foundation already.  

Is your soil the type that tends to "Settle" after the line is in, requiring a re-dig and an adjustment to get rid of bellies in the line, or is it considered stable.Are you allowed to oversize the line a little for a small upcharge?

Soil samples and tests?

Here's a qucik mockup of the garage more matching the house.That foundation, wow, what a mess.If it were mine I would have a structural engineer and maybe a soil engineer come out and give an opinion on it.It's sheer weight may have made it crack off like that, no rebar, etc...If it's was salvageable, maybe I would jackhammer away the broken parts and reset the walls on the good part. making the garage smaller.Disassembling and bracing one wall at a time and increasing the overhang of the roof.Then when done, gypsum board the entire thing inside and paint it ceiling white.If it were  my personal garage I would Pink Panther insulate it and use a space heater for winter comfort.It could be a nice little gym for renter who works out.Also, I would have an electrician verify the electrical is hooked up correctly for garage (because the concrete seems amateurish I suspect the electrical may be too).

@Sandy SandyIf it’s not a great neighborhood you will have higher vacancy rates and higher repair costs.

The waiting to dry in between (and light sand) is what is the most time consuming.And if I have time after a few weeks I'll add a clear gloss over the topBut if you have no money/ low money or just wanna save money, it's a great option. 

The other problem is the stats change, I do new soil farming every 6 months to determine changes and recognize changes in my research.  1. reasearch, research, Research your area2. set your criteria, ROI limits, and geo specific areas3. setup auto search systems or notifications4. rinse and repeat : Goto to step one

I was saying virtually no overhead if I'm just providing the soil they are parking on.

If your rentals are in Texas make sure you check out the local soil conditions.. clay and movement of soil is very common in many parts of Texas and its not if  its when your going to need foundation work.. 

For exaample - I would bet that rents in Roswell, Alpharetta, Sandy Springs, parts of Duluth, etc would be much higher than parts of East Point, College Park, Atlanta, etc- and they are in the same county - the schools make the big difference here- since drive times from the north are extreme as you know.