Are you sure it's rust?
Today, I have 476 miles on my odometer and the tail pipe side has some discoloration from the heat. They can't stay looking like they came out of a box forever, figured mine is normal.
If yours is worse looking than this picture I'd suggest having the dealer look at it. Is there rust starting anywhere else underneath? If so, I'd be very inquisitive as to why? Too early in the year for salt on the roads.