Can you negotiate the price of a bank owned home?
Everything in real estate is negotiable. However, banks are more sophisticated about pricing than they were years ago. So those "Get a great deal on a foreclosure!" days aren't what they used to be. Lowball offers generally don't go very far.
How would I go about finding someone to finance a sheriff sale property?
You have to show up with a cashier's check or certified funds. I suppose if you had another asset that you could borrow against AND you could get a loan large enough using that asset as collateral, you could do it that way. But you're actually financing the other asset and not the foreclosure property.