My partner is requesting repayment of the total of his cash investment, which I agree with.

I also told him to hold off on putting it on the market which he agreed, he’s totally okay with the wholesale process.

The numbers are obviously not pretty in the scenario you described. 

I try to buy under market value, obviously if it is something that is available.

Vanguard total stock market fund in taxable account (I ask this because I heard Dave Ramsey mention he puts money for real estate in an S&P fund until he’s ready to buy).  

Totally fine with online only banks as they seem to be relatively low headache.. 

Just a suggestion, I've had some luck using the approach; "obviously you don't like dealing with me, let's come up with a solution that works for both of us so that we can move on with our lives and not have to speak with one another ever again."

I would also compare what kind of high-quality rentals you can get in your area and what their cash flows are obviously. 

As I think though the Math...If a property that is worth 5.3 million today at 6% cap approximately, at 5% interest rate; if the same property I could get at 4.3 millions in 2 years if the market falls, then interest rate possible at 6-7%, my cash on cash may be better but still not significantly better due to the higher interest rate, plus opportunity costs of sitting on capital for 2 years (1.3 million investment earning 1% bank interest instead of 7% COC if invested, loss of tax break depreciation, total loss may equal 200k loss in profit), plus increase in the rents and some value add could increase the cap from current 6 to 6.7 or so.

This was primarily done so I could have more control over my own career/earnings, but I retained every aspect of the company (including it's 4 employees) and re-branded with a new name and mission as she was a great appraiser but not much of a businesswoman.I didn't have the liquid assets to buy the business outright, and it was a bit wonky in the math anyway since I was a top producer, my gross earnings couldn't really be factored in to the totals as I would have made that anywhere.