Here's the first decent listing I've seen under $80 sq/ft in Corona. 25285 Noble Canyon, this 5 bedroom, 3.5 bath home is 4158 sq/ft in size. From the pics it looks nicely upgraded and in very good shape. This one sold new, Feb 2006 for $716k. The bank now owns it and thinks that a listing price of $327,500 aught to git-r-done. That is about 54% off the new price, or a loss of about $388k. All in all this one looks like a reasonable deal. I'll give this one a green light if you can get it at that price.
If 4000 sq/ft is a bit much for you, you might want to look at 25215 Coral Canyon. It's just around the corner and at 3268 it a little more "cozy". Actually its still quite large but this one is listed as an REO for $285k. That puts it at $87 sq/ft.