Hi and welcome,
Sorry, afraid I don't know how much you get for renting for sheep. Only thing I can add is that our next door field to us rented out the field for horses to graze. He charged £1 a horse per day, and generally had 2-3 horses/ponies on a 2 acre field. However that price was 5 years ago, and also is from central scotland, I suspect the going rate is a lot more where you are.
Beth