loud thunk noise when braking

when i apply the brake there is a loud clunking or thunking noise and i can also feel it in the pedals. Could this be axle related problems or am i dealing with something more serious here? Im trying to sell my car andthis noise is seriously hindering my efforts, any help would be appreciated.

TIA

Try looking at your calipers to see if all the hardware is there and see if the caliper hold down bolt is there. One time, one of my bolts came loose and it made that clunking noise while braking. So if this helps any.