Very basically, figure around 2 to 3 dollars a mile plus all expenses for a good delivery captain. Some will work by the day, but it still works out to be about the same.
A delivery is just that, unless you arrange differently. If the boat falls below a certain speed, generally around 6 knots, then the engine comes on and stays on until the boat will make the speed without. Most deliveries are not sightseeing trips for the owners, or a leisurely cruise. Make sure you and your captain are on the same page on this.
I used to stack my deliveries pretty tightly, but occasionally I might be able to slip another in between trips if I didn't dawdle. That's the nice thing about doing ditch trips: the weather on the inside days was irrelevant. Up at dawn and running till dusk. Tie up in a marina, wash the boat from stem to stern and then off again at dawn the next day.
I would recommend that you look for a delivery captain through a reputable yacht broker. Most maintain a stable of excellent, experienced, honest and reliable delivery captains that they use themselves.