Jan Koum signed the deal to sell WhatsApp for $21 billion outside the former social services office where he and his mother once waited in line to receive food

Jan Koum signed the deal to sell WhatsApp for $21 billion outside the former social services office where he and his mother once waited in line to receive food stamps. In February 2014, WhatsApp co-founder Jan Koum returned to a modest, abandoned building in Mountain View, California, to sign one o…