If you've ever sat around wondering "why can't we just hollow out an asteroid, make it spin, and then live on it?" know that you're not alone. In fact, a research team from the University of Rochester did a semi-serious study of the matter and put together a comprehensive plan about how one might go about doing such a thing. It doesn't require any exotic tech (though it's a bit beyond what we're currently capable of), and would "only" cost on the order of $34 billion according to the team.