What might be the real life inspiration of Oda behind writing One Piece?
I would like to share this after some research:


  As a child, Oda gained interest in pirates through a famous television series titled "Vicky The Viking". He was inspired by Akira Toriyama, creator of Dr. Slump and Dragon Ball and aspired to become a Manga Artist. He worked as an assistant to different manga artists for a few years before finally starting out with One Piece in 1997.


references: 
http://orojackson.com/threads/odas-inspiration-for-various-one-piece-elements.1425/
http://onepiece.wikia.com/wiki/Eiichiro_Oda