I always hear stories about estate auctions and great deals people get on trains there. How do people get involved with that? Is there a website or auction house that tends to see more OS2R than others?
I have has some luck with Stout Auctions in Indiana. They are primarily a Lionel Collection liquidator, but there are almost always 2-rail goodies buried in the listings. i.e., this Thursday (8/13) there's an auction that includes hundreds of Intermountain kits and dozens of Korber structure kits. You need to scroll past a lotta Lionel to get to 'em ;-). There's always locomotives in these auctions that could be worth 2-railing if you are so skilled/inclined. This auction has a few Sunset 3rd Rail geeps that you might still be able to get 2-rail wheelsets for from Jay Criswell at Right-O-Way. He supplied me with a set a year or so ago for a Sunset SD-7.
I have my best luck on e-Bay. Despite being an O Scale modeler, I have collected 15 brass HO locomotives in the past year, all in great shape, some rare, but all unpainted. Unpainted brass seems very reasonable in HO (most expensive unit I bought was a $325 U50C and $250 for a TR4 cow / calf set, all the rest were under $200). Still looking to build out my collection of Alco Century locomotives in HO! I see less unpainted O Scale brass than I do painted O Scale brass. It seems that in both scales, painted brass commands a premium over unpainted. But to me, unpainted is a blank canvas, and hence, more valuable. The market suggests otherwise.
@rilynes I have also used Stout Auctions. Kind of fun but I have not been too successful in my bidding.