My starting point in viewing this car would be to inspect all the supplied invoices for work done throughout the life of the vehicle.
Next, I would have the car put up on a ramp to check for all the normal W124 weaknesses.
After that I would check all the electrics for functionality.
Then if I thought that purchase was worth pursuing, I would start the engine with the bonnet up and listen for non-normal squeaks/rattles before taking it out for a run.
Oh yes, I would have a mechanic with me who knew what to look out for.
I'll stop day dreaming now!