I have a roofer come inspect, and it happened to be when it was raining after a snow/ice storm was thawing out, and saw no issues whatsoever. 

With no contract and no receipt , you have no proof whatsoever that you ever had an agreement with him with no proof you have no case .  

The loan payment, not including property tax and insurance, on $500k is about $2500/mo.......kinda tough to afford on $300/mo income.no one is forcing you to work, but you can't force them to lend you any money either, that you couldn't possibly pay back.But, to answer your original question directly: with $300/mo income you can not get any mtg whatsoever. 

Assessed value has nothing to do with anything whatsoever as it relates to auctions.

Which is where you would be in my opinion if you went down the rabbit hole of pursuing this property based on the assumption of equity.The "original" loan amount means nothing whatsoever.

He told me  there are 3 siblings total including him, and he has no contact with or has any contact information what soever of the other 2 siblings. 

UPDATE AGAIN: DO NOT USE FOA COMMERCIAL FOR ANY REASON WHATSOEVER. 

Nothing else is different because they are using an agent whatsoever. 

From a second hand source (no ties to any legal bill whatsoever), it could not go over 1,200 sf and must not be less than 5' away from property lines.

Any advice whatsoever...