Just FYI, the metal used on brakes tends to get surface rust incredibly fast if they sit in moist weather. It's not a huge deal and it will all go away after a few times braking.
It's not the dirt you need to worry about with flooded cars, it's water getting into places it shouldn't for mechanical components, (transmission, engine oil, differential, etc) into the electrical system, and causing mold and mildew on the interior.
If you know what you're doing you can salvage flooded cars pretty successfully provided they are dealt with pretty quickly. You've got to start drying the interior and drain and refill any fluids ASAP. However the car will most likely come with a salvage title and a mention of flooding in its carfax and I doubt it will be sold with any warranty. Financing will probably be non-existent too.