See if it's a Euro (4 wheel hydropneumatic suspension is a give away among a bunch of other things)
Another member here had one, and to this day, is still glad he no longer has it.
In my opinion, $9k for an '85 is a bit rich. I will sell you my '88 420SEL for less than half (it has 137k miles)
-Larry
PS: You don't get alot of ponies with that 500...you get more with the 420