Upon entering the shack, turn left into the bedroom, the holodisk will be on the bedside table. To access the safe deposit box, open your Pip-Boy, start playing the holodisk, and immediately exit the Pip-Boy 3000, before or after interacting with the voice activated security system. The security system will tell you that you have been granted access the safe deposit box and it will open. The deposit box contains 4 bunches of pre-War money, and a sexy sleepwear.
Even though the terminal in the bank says that Bern is male, the holotape has a female voice, the same voice that leads you through the Velvet Curtain quest.
...Don't tell Evelyn. The Password? "Buttercup", Why...