I've googled and the best info I can find is that the water source is either from rising water, condensation, or penetration.

@Scott Weaner, I'm not familiar with these inserts, but my first thought was condensation build-up between the existing sashes and the inserts.When you say older, about how old are we talking about?

I figure these spots could be either from condensation or seepage.

I had an older condenser freeze up last year when a tenant set it to 68...

Let's say I upgrade my HVAC to replace old if install new condensation units worth $10000 just for the sake of numbers, how does it impact my depreciationWhat section of tax returns has information about depreciation.Appreciate your inputsThanks.

I've read bits and pieces of everything you mentioned in various places, but it's great to have it all condensed into one post to be easily digestible and for reference. 

The condensed version of the story is,  "The fence needs repairing, here's your estimate." 

.- Two weeks later she complains that her toilet is leaking again (she really hates toilets apparently), after my handyman (not the contractor) inspected it, he said that she mistook condensation for a leak.

I will try to condense this down to a simple scenario for anyone that may want to offer an opinion.A good friend and his wife and my wife and myself plan on buying on Maui in the next few years.  

SOMETIMES the problem is caused by the idiot who decided to put vinyl on OVER THE TOP of the old, maybe faux board siding.If there was moisture in the old siding it's going to manifest itself by creating condensation on the outside.