I am looking to buy a 1997 S320

Well, I think the W140 is probably the best car Mercedes-Benz had produced up to this very date, they nearly spent around 1 Billion Dollar s and even the first design team was fired due to an over costly budget:-) There isnt actually too many things to look out for in a W140 S Class but to be brief; 1) Have the car checked to see if it was involved in a serious accident that may have involved work done on the chassis. 2) Check for rust especially under the fenders and sunroof area. 3) Check engine and transmission since even if they may be asking 7900 for the car itself only a transmission rebuild could cost up to 2000 Dollar s. 4) Check coolant, fluid and oil leaks. 5) Make sure the AC is working good cause the evaporator in these vehicles have seemed to fail a lot and just for that the whole dashboard has to come down. 6) Check engine wiring; due to passing years the cables may fail and its hard to guess where the problem is and you may have to change the whole wiring system which looks like an octopus when removed:-) I guess thats about it, if well maintained and serviced its a lovely car which will still turn heads and its definately much more reliable compared to the next generation W220. Just keep in mind that even though the car may cost you around 8 K doesnt mean that the spare parts are cheap and if not serviced properly it may cause you to spend another 8 K to keep it running. Cheers.