When (or after what quest) do i get the key and who gives it me ???

Be on good terms with the Legion and talk to Lucius.

But I'm telling you, the safehouse is stuffed with all kinds of awesome shiznit.

Need a "Liked" reputation.

You need a "Liked" or higher Reputation to get the key.

I wanted in just for the lucky shades, but i can't bring myself to be associated with those people. Especially with Boone around.