Hello, this is my first post! This may sound funny but I have lived in Arizona my entire life and have found a deal on an 03 sl55 merc with all right options and colors i want, and only 25k miles. It's a two owner car and for the last 3 years and approx. 10k miles has been driven by the 2nd owner who lives in NY/NJ. If I want to drive it for about 4 years and then sell thereafter, should I be worried about rust? Is is hard to sell a car with that has a carfax showing it was previously owned in a rust belt state? The owner claims that its only seen rain 3 times, so i think he's implying he uses it as a "summer car". I've never had to think about these potential issues before because all the cars i've purchased previously were California cars. Will an inspection uncover rust issues? Is rust something you just cannot avoid with from north-east coast cars? Am I being paranoid? In the pic below, should i be worried about those two rusty looking screws on the lower left side of the pic?

Thanks for all the help!

 

welcome.
well the rust belt is notorious for cars seing premature rust due to the fact of the snow salt and other sea elements that go around all year round. Yet remember rain and snow are two different things. But with 25k on the clock ina 03, more than likely the owner is being pretty honest, yet not many people in some parts of NJ/NY drive much anyways. You can find a rusty example of a car just about anywhere so just like anywhere you have to take a careful look for rust, even more so for cars in the NE. Seeing you are in Arizonia, seeing the car in person might not be all that feasible. Hopefully he have sent pics of the under carriage and all the common rust spots. If not requets those. And a couple of rusty screws is usually not a cause for great alarm but is enough to take a closer look as it could point to bigger rust areas.
Ironically I was looking at S-class W140s and W220s in the Arizonia area. Probably will rid myself of the 300. Sorry I tried the American car thing and that 300 is nice but it's nothing like a Mercedes especially for what I paid for it. Plus you throw a rock and you'll probably hit another 300.