Fiesta is one among the 5 cars at home and used only on highways hence the low odo.
Regarding rust, yes, below both the ORVMs. No where else on the body.
there is a bit of sponge under both the mirror panels. this sponge holds water when washing or in the rains. remove the mirrors and get rid of the sponge. i had the same problem with my used 1.6 classic 2009.