How come James has posted the only sensible replies?
Number one is security. Number two is the thing you are gonna use: condoms. The rest is up to you, it's your paid holiday time so forget about pandering as she won't respect you for it or give you any freebies.
Security: not only have a lock on your case but lock the hotel door key in it. Or put the key in the room safe. Otherwise she can walk out the door with your dosh while you're asleep. (I have even better security tips for those that need them.)
Next, take your wits with you and be clear before you hand over the money that it's for a nice evening with sex for this evening AND tomorrow morning (and if in doubt, she will be paid and kissed on the way out once the transaction has been completed).