There should be more threads like this one.
I know this is crazy, out of the box stuff
Hardly. Your mind is just starting a journey that many have trodden before. Try reading some Stephen Baxter or Ben Bova to get you started. And RAMA has provided some excellent links to provide food for thought.
Regarding the rather depressing thought that we are stuck in the Solar system with finite resources - it doesn't have to be that way. The technology exists now, with some fine-tuning, to produce a "generational ship". Well worth reading about. Even at sub-light speeds we could have the galaxy colonised within a couple of millenia.