@Jesse StahlJesse I am not an attorney but what you are suggesting sounds and smells a bit like loan fraud.

Look at all comps for duplexes in area do not use single family identical structures and expect the same appraisal for a similar building

Look at all comps for duplexes in area do not use single family identical structures and expect the same appraisal for a similar building

So therefore no title company would want to insure this transaction as the former grantor can no longer be found and uninsured means potential fraud to the title company.

Concealing a fact to induce a lender give you a loan when they otherwise would not is considered mortgage fraud. 

I purchased the condo for $120k in 2013, I currently owe $80k, and based upon sales of VERY similar properties within the condo community, I believe it would sell today for $140k - $155k (immediate neighbor just sold their nearly identical unit for $153k).

You can always commit mortgage fraud and move out and not tell anyone. 

A homeowner has been in foreclosure for a couple years and has filed motions against the mortgage holder, its counsel and mortgage advisors asserting that they did not have legal authority to schedule a sale, that they failed to obtain proper, legal valid assignment of mortgage and power of sale, that the foreclosing party is in violation of Federal money laundering and wire fraud statutes, that there were violations in Truth in Lending, that he filed for bankruptcy, that he had a binding arbitration underway, etc. etc.  

We are too regulated, to tell the feds we are selling our bank owned property to person/entity "A", when its really going to person/entity "B", without putting the fake buyer that doesn't have the money to purchase the property (The usual reason this scenario comes about) by creating some fantastical wholesale LLC structure so they can get some crumbs, through the ringer with disclosures and warnings about real estate fraud (We love the "This contract may not be assigned without written consent" piece).

You also don't want to borrow money under the pretense that it is a personal residence - that would be mortgage fraud.