(and for the sake of argument, lets just say I can get it from the motivated seller for what ever price) This is the part I struggle with in regards to rentals because I believe I have grossly underbid some motivated sellers using the rehab formula to make my offers (65% of ARV minus repairs)

@Drew Feinis correct that a few details are needed - and possibly a few steps to notify the party of what you are about to do, why, and how to prevent it.

If they get 3rd party financing (can be hard to do with MH), you could use that cash influx to purchase more Mobiles and do improvements to the land.  

Be very conservative on your ARV (final sale could be 10%-15% below your asking), don't forget to factor in construction overruns and discovery work (typically budget a 15% cushion), don't forget to budget acquisition costs (6%-10% of purchase price), selling costs (6%-10% of ARV) and holding costs (be conservative it will almost always take longer than you think or than your contractor tells you and may take more time than anticipated to sell and for buyers to secure funding).  

The experience you will gain is worth much more than the money part.  I

Where I see projects fail is when owners don't listen to the paid expert party where the owner thinks they know better that the professional they hired. 

Most rentals with higher perceived risk can be offset by requiring an excess security deposit and/or a third-party guarantor for the lease, and/or prepayment of rent. 

As for now all costs have not been settled, but neither party are taking blame. 

We completed construction with a conservative valuation of $222k (I sold less than 12 months later for $245k).

I've used a third party site that indicates there are many tax sales/auctions (is there a difference) happening at several different locations throughout the county; anyone know how to consolidate this disparate locations through a single service (website?