Where can I locate bank REO properties before they are assigned to a realtor?
That would be a pre-foreclosure; aka a short sale. The only other way to get them, if you do not have a network of agents working for you to give you the cream of the crop deals post auction, is to be a cash buyer and purchase them at the auction. You can find out who & where these potential homes are from obtaining a notice of default list, and looking at the notices of sale, those are the properties that are about to be available for auction.
If you are not a cash buyer then working with the short sales is the only other way to get them before they are assigned to a REO agent, which is typically about 10 days after the bank can't sell it at the auction.
I hope this helps, please feel free to check out my profile and contact me directly for more information.