Going on HK's report ofd which I am aware of. I would like to add the following comment.
Slight rust formation on top of the rain rails has been known to occur, the paint is thin at this point also the metal surface at the highest point of the rail is not consistent in the smoothness of the metal.
A simple polish will fix it, as this is caused by an acidic presence in most cases eg tree sap wood, oil heaters wood fires etc, pollutants from industrial fallout.
Rust formation under the plastic steps can occur due to excessive and consistent moisture, there is a very simple fix, remove the step and spray with White Lithium Grease, this product covers all areas , as it dries it expands it will not wash off or freeze it prevents friction while protecting against rust and corrosion.
Roof seams rust, this is a U.S quality production issue it's not a normal occurrence for the Mercedes Sprinter, there has never been a registered complaint for rust on a Sprinter in Australia.
Whilst in transport it's likely oxidization has occurred and not been dealt with prior to re assembly at Ladston FL
All metal surfaces either bare or in base primer prior to repainting have a special surface metal primer reapplied to unpainted surfaces which takes a full 24 hrs to cure, before a two pack paint is applied,
Rust under screens the same applies if the screen is fitted on US Sprinters in the US factory screens don't rust underneath, unless it's constantly wet or damp, they can be cleaned and should be cleaned after each winter or at least twice a year, there are six points on the screen to run a air blast through to clean out the rubbish that may have accumulated CR3 is then sprayed to keep it in a neutral condition to prevent possible rust.
If the screen was not correctly vacuumed sealed when fitted, it could be a trap area for dirt to accumulate to generate rust, and this takes years for it to break through. if the water content is mineral free.
Hinges on back doors are fully primed and painted in two pack paint no Australian sprinter has paint falling of these sections.
No reported rust problems from data since 1998. they have a galvanized surface underneath or zinc primed.
Wheel rust, is either from salt! or corrosive impact, from an outside source.
Mud flaps are attached firmly with plastic screws not metal, there is no movement to create abrasion as such. but it is a dirt collector.
Paint on some areas where there is a silicone type seal can be effected where it may de laminate again a solvent is usually the course, but it can be a weak point, for paint to come off these sections is most likely caused by a human contact, with an oil like substance whilst cleaning with prep off... prior to painting again, pre-assembled in the states may be the quality issue.
paint on a hood bracket will wear or chip off , they do have a cadium plated surface underneath, , IMPO I don't see why they should have paint on them in the first place.
Rust in parts of FL, NY snow effected areas salt will rust a vehicle quickly if not kept clean. Desert areas surface rust, is common with high heat during the day and below freezing at night, it creates condensation! paint breaks down with internal surface rust forming .metallic paints first sign of failure is the clear finish peeling off or fading between the clear lacquer and the base coats of metallic based paints RED enamel paints are also a fade out problem , some also standard colors also have a clear lacquer applied over them too they are known to peel back.
Canada well that's guaranteed to rust a vehicle out in five years, if commercially driven on salt coated roads.
But for a vehicle to be parked in a sheltered garage six months old does not add up, unless its lives in plastic coated high humid presence, with a green house like atmosphere.
I would like to see high resolution photograph's rather than just a comment.
This is not normal for a Sprinter. under five years old and then it's a cleaning issue that created it in the first place, or lack of.
Richard