It is more cost effective to mortgage and refinance one property worth $150,000 than two properties worth $75,000.

Let them pay for what they use and they'll waste less. 

They don't care what the "real" value is and so paying for an appraisal is a waste.

I wasted so much time and effort with previous agents.

What are the potential pitfalls to this other than the obvious such as, I buy a lemon and waste a ton of my 401k money. 

Most banks won't do this small of a park so you'll want to start having that conversation with the seller about seller financing now before you waste too much of your time.  

HelloI'm currently in a position where I have signed a 6-month fixed term lease, paying $800 per month (effective January 1 2016) - with a three-month termination notice clause. 

It will have a negative effect on your credit score!

Ideally, it is the appraiser's opinion to utilize sales which have the most recent settlement dates, however, due to a paucity of settled sales in the subject's market area, it was necessary for the appraiser to widen the market search to obtain comparables with similar utility, style and effective age.

With the information you've given so far I would say send letters to every address you have.If it's a bank or mortgage servicing company and it's a large one, don't waste money on stamps.If it's a local bank, like HI only, go to a branch and ask for the REO dept.Good luck!