I have not seen a single ISF that has had rust at any age, so really just check for cosmetics, they really are pretty bullit proof so not a lot to check, water pump as mentioned but this should have been done, if they are willing to put it up on a ramp it would be worth checking the brake lines (the hard lines that run the length of the car) these can suffer with corrosion and are pretty costly to replace, check for any knocking or whining through the steering, there are starting to be a few issues on high millage cars with the steering racks, this hopefully should mot apply to such a low milage car.
she looks a beaut btw!!