@Odie AyagaNothing in concrete.

One of the contractor told me that he will put pressure treated wood to support 12 floor jacks across various places in 20X10 basement area and make a 3ft deep concrete base to place jack post to stop settling for $6200.

Must be on a permanent foundation and with concrete skirtings and in some states hurricane tie downs.  

We chose just below median priced single family homes in nice areas where there was just a little bit of polishing up to do to make it a great modern home for families.

In the next month we will be completely replacing the main sewer line (which involves cutting a big whole in the concrete basement :D) and replacing the roof and gutters.

I don't know the area so it is hard to say but they is a crazy long time for a unit to be vacant if it is priced right.If you know someone nearby I would have someone pretend to be a perspective tenant and go meet your PM and see what they think.I would be marketing the unit online wherever you can and just put the contact info for your PM until it is filled.I think you need some concrete answers from your PM on why it is not getting filled.

I don't think they would be willing to take the contingency of selling the investment property first but its worth a shot before I say anything concretely.  

Same for our Concrete contractors. 

It could be stone, concrete slab or blocks.

The cosmetic repairs are a new driveway, new landscaping, new plumbing in part of the house, new sewer line under the slab due to tree, removal of tree, renovation of the onsite storage units, and some concrete work for the walkways and the backyard of one of the units.