2007 Subaru Legacy Rear Wheel Grinding Noise

Hello, everybody. I just bought a 2007 Subaru Legacy 2.5i, when we test drove it there were no noticeable noises. However after I picked it up with a tow truck and took it home I notices, a grinding noise around the rear wheel, it feels like its holding the rear wheels from running to their full potential. Every time I drive the car the noise is consistent, it will not stop until I come to a full stop. My brother has told me he noticed something hanging from the rear of the car, he tried to place it back to its original place but it will no. Now I am freaking out a little bit, I do no know what to expect nor can afford to drive it to work. Does anyone here know what can be going on? How much it will cost? Any ideas? I know all the fluids are filled and changed it even passed inspection today, yet I am still worried.