Is it hand brake or rear brakes? If hand brake lever moves down, rear brakes are stuck, could try rocking forward/ reverse, the van that is. Using the gears, might free it, if not, wheels off, and then get to brakes, but still need to free them to take drum off for cleaning, Or could be cable siezed in the guides. For that, turn the adjust ment off, which will get you moving, to nearest parts depot or garage to get it replaced.
SD
September 2011