Hi, I'm about to purchase a 2001 Mercedes Benz SL500.

If you like the car, purchase it. It's a 14 year old luxury car with a lot of extra moving parts to make it more luxurious. Those parts fail/break, are expensive to replace/repair and are a lot of times not 100% related to driveability of the car. One common item like that is the secondary air pump on the car. Fails very often and really does not hinder the car from running but keeps the check engine light on. If you are buying as an every day driving car, not a car I would recommend, regardless of price.