Without getting into the nitty gritty, I am new to this, but I'm partnering with someone who is very experienced and has a dozen flips under their belt.

I would see how the home inspection goes (get someone good) and make a assessment than on how you want to proceed.

Not sure how they could block a sale but I imagine they told him the central heating unit for the whole complex would soon need replacement so a special assessment would be upcoming.  

The coverage limits are as follows:$200k -> Dwelling Premises Liability -> $300,000 per occurrence Medical Payments $500 per person / $25,000 per occurrence Additional Living Costs And Fair Rental Value -> $19,000 Loss Assessment Coverage -> $1,000 Ordinance or Law -> $20,000 or 10% Water Damage Limitation -> 10% ($20,000) Deductibles All Other Perils -> $2,500 Limited Theft Coverage -> $2,500 Water Damage Deductible -> $5,000

I also agree that RE appreciation is unlikely to match the last dozen years, but you never know.Where I am unsure we agree is that paying $450k to improve the cash flow ~$3k (your numbers but I expect my delta wold be similar meaning both my cash flow estimates would be worse than yours but both would be worse by the same amount not affecting the difference) makes sense especially if the cost of having the extra $450k is only 6% rate which is historically simple to beat via numerous investment options and hopefully no one is investing in RE for an expected of 6%.  

And if not, what other suggestions would you have for getting the comps I need to accurately assess ARV on flips? 

Bought under assessed value, slight value add through cosmetic rehab (paint, light fixtures, flooring) What was the outcome?

The above also doesn't cover the dozen times I asked via email and phone for more regular communication.

It's a lease, not one of those clean energy assessment lien crap things.

There are a lot of cheaper areas in the Midwest and South where you could take that 500K and buy either a dozen or so properties (with a DSCR) or buy a bigger multi-family.