l am thinking of buying that car for my sons first car. Is this a good idea? It has almost 200K miles on it and is in perfect condition since l know the owner and how he takes care of it. Pleae voice your opinion. Thanks!

It will be a gas hog, but it will also be an extremely safe car for teenagers to ride around in. Mercedes in that era have a great reputation for safety & reliability, there r a lot of older S-Class cars out there that have gone over 500,000 miles. As long as ur son will drive it u have a winner! A few years ago l bought a 1976 Olds Cutlass Supreme with 63,000 miles for $2,000. (a steal of a deal!) because the teenager it was intended for was ridiculed at his high school for driving a car that was not Japanese!

Put a new timing chain on it,and clean Cats. out.

Eh, pretty safe but too much power for a kid and his buddies to cruise in. I'd find him an old Buick LeSabre, just as big inside, good power, better on gas, insurance will be less. You sure the kid is not trying to talk you in to this?
The 420 is known for eating timing chain$$$$$

as a suggestion perhaps u purchase the car & u make child purchase tires, alignment & fuel [this keeps them from doing burnouts & keeps the speeding down], & promotes better general care & responsibility.
while this is A-LOT of car for a short time driver it is a safe one [IF SEAT BELTS ARE USED EVERY TIME THE CAR MOVES]
this car is due for a timing chain replacement by mileage, & suspension components & bushings should be looked at closely with a jaundiced eye