Diesel Mercedes W123 models are notoriously endurant cars, lasting well into the hundreds of thousands of miles. If it's the classic Mercedes look you seek, I'd recommend one. They're most commonly found in models: 200, 240, 280, 300, 350, etc. If you find one in good enough physical shape with around 150,000 miles or less it makes a great initial purchase. But if you don't plan on disposing of it when something breaks, the price will catch up to you very quickly. A twenty year old Mercedes is still a Mercedes so maintenance costs are still high as they were in 1981.