I've got money in one online character account and I want to transfer that money to my other character. Is that possible?
No, not directly.
As always, there is a "workaround". You can challenge a friend to a match (arm wrestling preferred because it doesn't take long), bet 10k and let him win. So he gets the money from you. After that, you log onto the other character and do the same again, he bets 10k and lets you win.
Of course, it takes a while, but it's the only known way to me how you can transfer money.