To this American English speaker, the meanings are exactly the same. Get back in this sense means "retrieve", and as you have written the sentences, they're both imperatives, commanding someone else to retrieve their money. Neither one implies anything about whether the money is really yours or not, or whether you are asking for it or returning it. Maybe you're confusing it with "Give back your money?"
The first phrasing is the more common one. When you make a sentence like that, you can think of it like
Get (get what?)
your money (get your money how, or where?)
It is certainly possible to change the word order, as in the title Gimme Back My Bullets, but the first order is the more common one.