I am considering purchasing a '99 Merc SL500 with 9k miles on it, it is flawless in every respect!!! - But I would hate to find out that it depreciates $10k once i put another 5k-10k miles on it within the next year or so. Its being offered at $44k, is this a good buy? Is it a good idea to buy this car?

Don't pay any more than $28000 for it and buy only with under 50,000 miles, You can get much better deals if mileage is over 50,000, because that's when expensive repair costs start I'm buying a similar, probably prettier sport-package 1996 500 SL tomorrow for $12750 after tax. I'm paying cash so I leave space open for future ridiculous repair costs. They pretty much drop in price about $10,000/year for the first 5 years then, afterwards, price depends on mileage and condition.

Oh, just noticed that this car has 9000 miles, in that case it's worth about $37,000-40,000. but it'll drop about $2000 for every 10,000 miles you add to it, which is still nice for a car of this qulity and performance.