Can't get in to dark brotherhood

I have completed the quest where you help the boy in Windhelm by killing the woman in the orphange and returned the quest, but I have not gotten the note and therefore cannot start the dark brotherhood questline.
Are there some other prerequisites in which case which?
And if it is just a bug, is there any console command that might help?

Simply find a bed and go to sleep. Sleep for around 10 hours and when you wake up "I don't want to spoil it"

You'll need to manually mark your stage as completed by using the following command:

'SetObjectiveCompleted <1 to set, 0 to unset>'

I found the quest ID and stage for you, so simply type this into the console:

SetObjectiveCompleted DB01 200 1

This will force-complete the quest. Then sleep in a bed for 24 hours (just to be safe). You should move on to the next quest.