This question seem pretty naïve for someone that's flipped about 30 houses. 

You see a boat jetting across the bay and then he walks into a luxury house.   

I think some folks search for discounts so that's a way for being promoted.Seems guest dont rent a 4 bedroom house unless they have triple the amount of guests they originally reserved for.  

Sure enough, the door was left unlocked and the house is just full of trash and abandoned junk.

They will find a first time home buyer that will be happy to pay close to what the neighbor's house (in great condition) is worth.

I wonder who still makes houses like this.

As others have said, the best thing your son can do is run far from this deal, buckle down, save his pennies (he probably already is doing this), house-hack, and improve a property with sweat, hard work, developing a DIY skillset, and self-managing tenants. 

Of the many strategies I've looked into, House-hacking and short-term rentals piqued my interests. 

Purchase price: $232,000 Cash invested: $200,000 Sale price: $575,000 I purchased this single-family property and undertook extensive renovations, including excavating a new foundation and reframing the entire two-story house.

Lake house, cabin feel, waterfront etc.