If the US dollar collapses, the value of that mortgage ON PAPER is going to drop like a rock.

I know, I know - I'm insane for thinking that the economy is a ponzi scheme and could (will) collapse.

Seeing as, on a national level at least, prices have only gone down twice since world war 2 (1991 &the housing collapse), why do you think prices will go down during a recession?

Walls that are collapsing inward should be "raising the roof", so to speak, unless it's some odd house without bird-mouth cuts.

I live in CA, and like many investors, when the RE market collapsed here, I looked around for a better market to invest in.

The Federal government pumped billions into Fannie Mae in the last real estate bust to prevent its collapse, and it would be a disservice to taxpayers leaving 3% mortgages on the books that shouldn't be there. 

Unless you have an inside scoop, you don't know if the basement has had standing water for 6 years, rotted sheet rock, and black mold throughout, or maybe a collapsed side sewer line.

When that happens, rents collapse.  

There's no guarantee in business, except FDIC insured, and that's if gov. doesn't collapse :-)Can gov. collapse during recession ?

If you remove them and the roof collapses, they were necessary.