Subject to - Podcast Episode 106 Question

[Martin Sterling]

Regarding Podcast Episode 106

If borrower is behind and the property is worth 100k.
They owe 75k on 1st Mortgage and 35k on 2nd Mortgage, the interviewee said he will get the 2nd Mortgage for $1500 because lender won't get anything in an auction. 

1 - Couldn't the 2nd foreclose? Why would they accept $1500? 

2 - If property goes to auction, doesn't lender on 2nd mortgage have the right to bid up the price to the amount needed to cover their loan?

3 - The Buyer (interviewee) short sales the 2nd mortgage and took over the 1st Mortgage subject to?

4 - How do you short sale a 2nd Mortgage? What is buyer buying and why?

Thanks!