Very minimal.  A paragraph or two should do fine.  I don't see much point in having much on the CS as they are going to be grouped, I'm sure that most of it will come out in the rp, so no need to write it twice.  Kind of adds to the anticipation and expectations they might have when interacting with one another, saves a bit for surprise.  Also go very minimal on equipment and stuff too.  There will be lots of item acquisition later on so. Thieves should pack light anyway.