I have seen worse. The tank plate holds salt and dirt and will rust out first usually, someone recently replaced this tank holder/plate on this site. I don't think the frame looks too bad. I would hire a hoist and take a few days with a wire wheel. Then paint over with POR-15 rust paint. Prep is key. I wouldn't touch the vehicle if there is any rust on the body but frame is ok if it's not too far gone. Still rust is always a pita and it's better to work on a vehicle without it.
While a southern truck is preferred for obvious reasons, some of us living in rust belt areas have very limited choices. I've had my truck for a while now (5 years) and sure it looks similar or worse than the truck pictured, but the build quality and rust protection in most important areas allows me to continuously enjoy driving / wrenching and not worrying too much about the evil brawn / red "substance". For comparison I also have a 2000 Tundra and rust on the frame (replaced 2 years ago and known problem) and other parts of chassis was a lot faster progressing than on the LC. Check for rust related problems, but also know that these trucks will last a long time even with some rust and for the most part it will not affect your driving enjoyment.
Looks fine to me. I have been driving mine in the rust belt for 16 years and it looks worse than that. However, nothing breaks so who cares? Body looks great and I don't spend much of my time laying underneath ogling my chassis.
How long is someone going to realistically own one of these things before they decide to move on to a 200 / 300 or whatever?
Yep, there's rust underneath but nothing on the body and nothing that was really disconcerting. Not planning to pass it to my grandchildren or anything.
It's a gray 2000 with 151k miles. Solid interior. Got it for $7550. Such an awesome deal, a little undercarriage rust was not a breaker. I'm really stoked. Drove it 4 hours home from middle of BFE Georgia, back to Nashville, and it performed flawlessly.