If you must have one lease them only and keep under warranty and return before the warranty expires.  These are all overengineered German machines full of technology and will cost a small fortune every time something breaks or needs repair.  Also, companies like Mercedes know the vast majority of people lease their vehicles so they cram a lot of technology and features into their vehicles so the lessee will continue staying with them as well as get new lessees.  They are not in the business of making vehicles that will last a long time without breaking (like a Toyota or Lexus).  Also, good luck finding a competent mechanic that can work on those vehicles (especially with all the electronics) - if you find one they will cost more - and if you have to go to the dealer the y will definitely charge an arm and a leg.