If you have a '95 or older Mercedes, a $1 electronic LED is all you need to read and erase diagnostic codes. For these cars one might not be able to justify the purchase of an expensive scanner.

For newer cars Carsoft is probably a reasonable choice. But rather than spend several thousand dollars for a product direct from Carsoft, one can get a Chinese copy of same on eBay for just $100-$220. I can conditionally recommend these, and I wrote about my experience here: http://www.benzworld.org/forums/r129-sl-class/1315950-diagnostis-later-cars.html?.