You can find the entrance just west of Falkreath, under the road, but you can't enter without the correct password. To start the dark brotherhood, go to windhelm and in the east side, there's a little boy who mentions that Aventis Arentino or something is doing the black sacrement, blah blah blah go in the house accept the contract. When you kill the target, go to sleep (in a bed) and the dark brotherhood will find you.
Hope this helps
Yes, you can.
Yes, the Dark Brotherhood is in Skyrim. You can get information on who to contact about joining them from the first town you arrive at.
There are no others you can acess other than the 1 in cheydinhal
It is given after Dark Brotherhood quest "Breaching Security"
You have to go through the Dark Brotherhood questline. Innocence, my brother.
You need to kill the old woman at the orphanage in Riften.
No, that's not necessary.
There does not seem to be any mention of a person called Binyamin as a part of the Dark Brotherhood in Skyrim. There are mentions of people named Benjamin who write walk through websites for this game.
it never ends idiot
Yes there are some but there are some in houses so be careful!
Factions you can join: Companions College of Winterhold Dark Brotherhood Stormcloaks Imperials With the Dawnguard DLC: Volkihar Vampires Dawnguard
No, I have finished Theives Guild and Dark Brotherhood and nothing's happened to either of the factions.