Check self storage auctions. Sometimes if there is good furniture or items in the house the trashout companies will store them for a month in self storage, send the previous owner a notice and let them know if they want it they can get it or pay the storage fees. They probably don't often do this and then you can bid on the self storage units as they come up for sale after non-payment.
Furniture in the property belongs to the owner of the property or the tenant if the home is rented. These personal items are removed when the occupant moves out. If items are left behind they are usually removed by the companies hired to clean up the homes and make them ready for sale.
If you want used furniture I recommend Craigslist.com