As with any expensive GT (Grand Touring) class car, it is my opinion that one should buy the newest and least mileage car one can afford, which is what Bruce Anderson of "Porsche Excellence" fame always emphasizes. As noted above by others, a nice M3 that hasn't been "rode hard and put away wet" should cost around $25,000 and have low mileage say in the 30K-ish miles range. Now, my experience won't mean your costs will be the same because we all make different decisions on how well a car should be maintained. I'm fairly anal about my maintenance but some others are not, so there will be a cost variance.
