Discussion - Religion or Cult?

Imagine your brother or sister tells you he or she is leaving home to join a religious group that requires the giving up of all possessions and money to the head of the group. They also require the wearing of white robes and separation from contemporary society. What would you do in this situation? Would you try to "rescue" your sibling? Or should they be free to give up everything if that's what they want? In this discussion, comment on what you think are the differences between a religion and a cult, and why that matters.