The water will probably follow soon after since the bill is in excess of $50,000 for the complex.

Whatever you gonna charge, it's gonna be "too much", and you are going to be portrayed as a "ruthless predator who charges excessive amounts for minimal jobs just because he is a relative".I'd personally stay away from dealing with relatives on money matters.

When I started working on the deals I had on the table and thinking about how I could use that money to finance those deals to fetch returns in excess of 35%-40%, it was a no-brainer to just finance as much as possible.

That means he will likely have plausible deniability for the damage, as he can just claim that his contractors did the make-ready and never informed him of any mold/moisture issues.

I know the boiler needs work--it worked last year but was putting out very excessive levels of CO.

The next level beyond that would be to invest internationally.For me I would value more highly having a brand in a specific city and be able to exercise economies of scale with contractors, materials, etc. over ensuring that I am hedged against any type of economic changes.At some point I think it becomes a "chicken little" type situation. 6 units in 1 city does not seem excessive to me.Another simple way to diversify would be to invest in different types of units.

Seems to me these charges are excessive, and give pm an incentive to have as much repair work as possible (in fact, there have been numerous repair works on my property so far.)The property is old (built in 1958) located in Atlanta.

Any bank will normallly let you make an offer contingent on a moisture termite inspection.  

in excess of $100,000!! 

I'm not familiar with Allure flooring, but if it's practically water proof as noted by @Edward Mccracken, then, as he indicated, the moisture is likely collecting from below the sub-flooring (be it a crawl space, basement or sleepers on a slab) and building up underneath the Allure (e.g., waterproof = impermeable).There doesn't need to be visible standing water for this to happen either.