Agreed, rust will be the main concern point, assuming the car isn't currently running (and therefore no ability to check for overheating or proper HVAC function).
If you do decide to purchase it, plan on replacing the timing belt and water pump immediately, unless the previous owner has documentation of it being done in the last 7 years (which I doubt if it sat for 5+ years).
You already mentioned bad brake lines. Other rust to check would be fuel tank straps, engine cradle, and general underbody rust, particularly at the front and rear subframe hard points. If the car was sitting in the driveway or on a concrete pad all this time then it might be fine, but if it's been in the grass, then it would all be suspect. Grass-storage is always bad for any car.
2002 Chrysler 300M Special - Deep Sapphire Blue/Storm Gray Metallic - 142,000 miles