This came to me after reading that a black-hole that has the mass of the observable universe will also have an event horizon that covers the observable universe.

Since the definition of a black hole is that nothing can escape from it, does it actually require for it to have a single singularity of infinite density?

Or could you arrange a theoretical black hole from a super-galaxy, or a dense cluster of galaxies, where they have so much mass that you can't escape outside, but at the same time you can "live" inside without being ripped to pieces?