The rear 25% of the lot (same with the 5 neighbors next to me) is considered a detention pond so it has a gentle slope/swale.

Trying to save $1200 (gently used) while dropping the price tens of thousands? 

And unfortunately it caused moisture in the return, which led to the heat pump to start rusting. 

Make sure you eliminate ALL moisture and wood to ground contact issues to help suppress future issues as part of the pest management plan to resolve your issue.

Just a thought, but what about dipping one's toe in more gently by buying smaller complexes, rather than putting all your eggs in one basket?

So really we just used Freddie, on a mere 1 of 6 loans, to bridge the gap between 4 Fannie refis and 1 Fannie purchase.And took this dude out of the loan shark world, bringing him BACK into the soft money and gentle interest rates world.

I have used it before, mike, and in a perfect world a cheap roll on product would do the trick, but all my moisture puzzles in the real world are so much more complicated. could be so many things, like where is it coming from... mere warm moist air condensing on cold places, a leak, slope or gutter problem outside, or an more costly drainage issue that means excavation around the house (for example., have you seen Holmes on Homes when they tackle tricky basement moisture the "right way" ).... so I would study it more (alot) and even think about experienced or expert opinions to find a source and craft the best solution.... wish I could say it is a 30 dollar and done deal....

Depends on your soil type and moisture. 

Any and all resources regarding this information are greatly appreciated.I am completely new - please be gentle!

Due to the HERS requirement of spray foaming the basement along the rim/band joist, air flow was nearly non existent and with some moisture in the basement due to the old stone foundation, it became an issue.