At 21K miles, you really can't go wrong unless someone has beat the living snot out of it, and even then, hard to find issues at this stage. I would start it and shut it down several times. Then take it out and accelerate hard, get it going as fast as you're comfortable, or as the current owner will let you without shitting his pants. Then, hook it up to a scanner (via OBD2 port). If no check engine light, then theoretically, should be showing no codes.
Look at the brake rotors carefuly. If you see any bluing, beware. Car has been driven hard. Check the condition of the motor oil; should be nice and clear and (at 21K miles) have ZERO smell of fuel. If you do purchase it, goes without saying to never put anything but a high quality full synthetic in it. Newer cars that see a lot of highway miles will burn a little oil - very little, so if you're mileage is mostly highway - and ESPECIALLY driven at higher speeds (if my Speed-O isn't reading three digits on the highway, my car gets confused
), or figures my other half is driving it - she thinks 80 is living on the edge - and next oil change (every 5K to 8K with a good full synthetic) you're down a quart or less, don't let it throw you.
Biggest issues on a lot of Lexus vehicles is stupid little oil leaks (VCG, TCC). Not a big deal, just a PIA.
Again, at 21K, its a new car.
Good luck !
Tim
