If it has been maintained by a dealer, get the VIN and have them print out the repair history.
Having the engine compression checked is a reliable way to find out how well the motor oil has been maintained. Also, when is the next major maint. due and how much will it cost? How are the tires, etc. This will help you estimate future costs.
You might go to the local library and check out some old consumer reports buying guides to see if that model made the "reliable used car list" or not.
Ask the owner if you can view the maint. records, if available.
If no records available, I would walk away.
check edmunds.com or kbb.com for blue book pricing.
Just my 2c.
Oh, if the owner is a little older, the car prolly has not been just been kept shiny and then raced to death.
2004 E60 530is, Delivered 12/12/03, TiSilver/LGrey, PP, SP,PS, PDC, ACC, FRS, Step, Xenons, clear bra, body colored rear inserts. (Retired, 1983 henna red 320is)
2004 Corvette Z06 Commemorative Edition