What model year is it?
Define well mainteined. Are there maint. records available proving this. Who is the previous owner? How hard was it driven?
It should be checked out by another dealer or independent mechanic.
ConsumerReports.org has reliability data on most cars. It's worth the subscription. Your library will have the print version.
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