So, two different issues, suitability for a 16 year old, and maintenance costs for a 180k mile LR3
1. Suitability: Outstanding. I sold my LR3 to a guy who continued to drive the crap out of it (lots of off-roading) and then ultimately passed it down to his daughter. She totaled it in a crash, and walked away without a scratch. It's built like a tank. A full body on frame design, with air bags everywhere, and Saftey beams in the doors, and all that. Excellent visibility, excellent brakes, superb turning radius, great handling (low center of gravity), and terrific traction and stability systems for implement weather conditions. It even has a decent sound system (terrible cd player though), and unparalleled flexibility in cargo and storage options. I might suggest removing the 3rd row because you really don't want your teen to be driving 7 people all at once, but that's entirely up to you.
2. Hard to say. You would think with that many miles on it, all the major maintainence would have been done. The V8 is really reliable, though there are a few plastic bits (coolant hose joints) that need upgrading to aluminum. Brakes are stone simple to change, and all the major maintainence is pretty straightward to perform, other than suspension calibration. I highly recommend a GAP DIAGNOSTIC IID TOOL to stay on top of the electronics. Transmissions are incredibly expensive, and there was a run of rear diffs that needed servicing, mostly all done under Warranty. Don't skimp on oil fluids. The factory periodicity is way too long between changes for all the components. Oh, the seat leather is crap. A nice set of seat covers should be in mind should you pull the trigger on this thing.