I don't know if it is rain or possibly just condensation due to poor insulation.

The sale typically makes no difference.....the condenser lines run up the exterior wall next to the compressors, then through the attic.  

Low-end A/C condenser and gas furnace installed will run you about $1800 and up...Average heat pump installed will run about $3500 and up...40 gallon gas H2O heater at Home Depot will run about $450, plus another $40 for an expansion tank.

@Rusty Thompson  in the cash flow markets it takes a special person that wants to be a PM in those asset class's I know many PM's won't handle the C D properties its not worth the time effort and headache. they cannot control that tenant demographic and they get skewered by the owners as being the bearer of bad news and the scapegoat or fall guy.Whats a Pm to do when your unit has been hit for the 3rd time in 4 years.. or your condensing unit was stolen again..

That's a whole lot of years of rent-profits all condensed AND best part, I can use it tax "free" (1031 for pyramid to expand rev gen base). 

I realize I'm from South Bend but my guy is usually in the $3k range for line set, 2.5 ton condenser, and a new evap if everything is easy to get at.

That is, we get condensation on the underside of the plywood of the roof and that molds.

From our long conversations about investing, I remember two things; whatever the life expectancy is of the products you use on your houses in Vegas, reduce it by half. 30 year roof = 15 years. 10 year condenser = 5.

@Simon ShihDoes $5-7k included condensing unit, ductwork, and new electric service?

It sounds like what you have is condensation that's probably stemming from an underlying insulation problem.