I am unsure as to the foundation of the cottage, but the modular portion appears to have been a poured slab (approx. 5" deep) with concrete block skirting. 

It sounds like you're diving deep into the numbers, which is great.

After attending an awesome BP meetup in Philadelphia (hosted by @Troy S.) some red flags have come up regarding the structure we're looking to use to fund our first flip.My partner, @Phil Sabella, and I have connected with a financier/partner who does JV's.  

Sellers did not allow us to get professionals in to give estimates for a french drain before closing (yes, our red flag we should have walked away with), but agreed to lower closing price. 

A few of my red flags: He didn't call me, she did. 

There was an interesting post on Realtor.com - https://www.realtor.com/advice/home-improvement/deep-theme-d...It is all about the creation of themed homes and rooms.

I agree with the answers above and that condos have a lot of red flags for STR investments.

Less governmental involvement, restrictions, fees, red tape, etc. here in SW Florida. 

Use caution and build a solid team before getting too deep into a rehab is my best advice.

Your buddy hired a pretender, so they got a bad quote.A quality PM has a deep bench of honest, proven contractors.