2004 Mercedes Benz E320 4Matic
You say it's been well maintained, so hopefully a lot of the maintenance from around 100K was done already.
At 124K miles, you should anticipate some suspension parts replacements. Balljoints and bushings will probably be worn unless replaced in the last 30 - 50k.
Don't pay more than USD13k for it, and probably less.
Check, or be aware of:
1) SBC electronic brake controller repair/recall history. It doesn't matter much if it has or hasn't been replaced under the 10 year warranty that applies to that part, but know the vehicle's history so you know what to tell the dealer if you ever get a brake warning on the dash
2) Transmission fluid been changed in the last few years? Brake fluid?
3) Spark plugs will need to be replaced if they haven't been replaced before
4) Transmission may have a leak from the eletronic hookup point. It's a cheap part and cheap repair, especially if done during a fluid change
5) The headlights probably have clouded up. You can polish them with varying success
6) It has very probably had brake disks by now. If not, you will surely need them in the next 3 years you want the car to last
4) If the seller can't give a clear history of them, change (1) the rear diff oil, (2) the transfer case oil, (3) the transmission fluid, and (4)the front diff oil . These are four different jobs.
5) The sunroof opens and closes without complaining
6) So long as the oil has been changed every year/10K and always used Mobil 1 0w40, then the engine may be fine, but listen for a water pump or pulley tensioner/bearing that may need replacing by now. DIY is pretty cheap.
7) I could go on...but I think mine have been reliable



