SpaceX Plans to Send People to Mars by 2025 and Elon Musk wants to personally visit space by 2021

Elon Musk personally wants to visit the space station within the next five years and thinks that his company will send somebody to Mars by 2025.

Speaking at the StartmeupHK Festival in Hong Kong this week, Musk said that he had already taken parabolic flights to prepare for space, but had not done much else.

There is a defensive reason for becoming multiplanet which is to protect humanity from a single planet extinction event
Establishing a city on Mars would be a great adventure for humanity
Mars is where a sustainable city could be established
Spacex is scheduled to a launch a crew to the space station by the end of 2017