I agree w/ the last post. There are plenty of cars out there. If you have your heart set on an 86 420 sel, that may be different. But there's no need rush into a mercedes purchase. They ARE expensive to service.
Here's something that worked for me.
Go to ebay.com and select passenger cars. Then on the left you can limit your radius to, say, 50 miles from your zip code. There are a lot of mercedes that are going fairly cheap (the diesels are selling for more than the gas burners). You can also restrict the bid price range from 1 to $3000, or whatever you want. By and large, I've found the descriptions matched up with the actual car pretty well.
Anyway, good luck with your new 'old' car, whichever you decide to buy.

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Love driving my '77 450 SEL!
124,000 miles