Escort, hooker, lady of the evening, etc. You should probably take the "romance" part out of the transaction.
If you go there clear headed with, I am purchasing a service, she does not love me and I am not afraid of spending some money to have sex attitude then you will probably have some fun.
If you have some little voice in the back of your head thinking wow, she is hot maybe I can keep her, you're fucked in the most literal sense.
It's a business transaction to her, that's it. Unless you hit the lottery and she sees your picture in the paper, then you become an investment.
For romance look for a girlfriend, not an escort.