A strong second to all the above. Make sure ALL the little bits work, such as AC, cruise control, windows, and radio antenna (usually an easy fix). Sun visors are expensive to replace if deteriorated, but easily fixed as a DIY if floppy. Check for rust in the top well and in the spare tire well, on the rocker panels around the jacking points, and one spot I hadn't thought of--the bottoms of the doors on the horizontal part, inside of the exterior panel. Inside the car, if the carpets are loose pull them up to check the floor pans inside. Check the parking brake; it should release easily and completely. Check the neck of the ell fitting on the top radiator connector; it's plastic unless an all-metal radiator has been fitted, and is a known weak point. The fuel pumps often are mildly noisy, but it shouldn't be loud or unsteady.
No matter how clean it looks, sounds, and feels, plan on $1-2K to fix stuff if you need the shop to do all work; if it's got "a few things" that you notice, plan on $2-3K.

__________________
Craig Bethune

'97 SL500, 40th anniversary edition

'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)


SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)