No, No, Yes

Forclosure 是银行在卖吧？No, foreclosure is sold by county sheriff. 

能讨价还价吗？ No, it is live auction aka bidding. 

贷款会不会有麻烦（其实才 2001的房子，估计屋主大兴土木还不上贷款）？Yes, foreclosure is usually due to mortgage default. 

Lifecycle: Mortgage default => foreclosure => sold by sheriff => most times the lending bank buys the house back => REO sale (bank owned real estate sale)

I think you are confusing the foreclosure sheriff sale with the REO sale.