The assumption that this is a brain wallet could be wrong. It could be a ROT13 type thing and say something outright without being related to financial stuff.
Assuming it's a brain wallet gives us a list of techniques to crack it.
Assuming it's a QR-Code gives us another list of techniques to break it.
Assuming it's a love letter written to Charlie by Wynona Ryder would give us another list of things to try out.
It could be ANYTHING. All we know is that it is not what it is trying to portray it is (a typical note from a paranoid schizophrenic delivered to a celebrity).