Rust of that nature in a modern car is totally unacceptable. I would be demanding either a new vehicle or refund - no company can expect a customer to accept that typre of defect as it indicates the body somehow missed out on the factory rust prevention process. Who knows where else this could be occurring that you haven't found yet? That isn't just water leakage, it's bare steel, and lots of it. As the dealer is typically passing it off as normal, go up the chain and see the dealer principal, the owner of the business. If still not satisfied, the Zone Manager is next, but DO NOT ACCEPT ANY EXCUSES FOR INACTION. From what your pics reveal, that vehicle is unfit for sale and should be replaced, not patched up.