I got my 500E at 120,000 miles...I've spent thousands fixing and upgrading stuff when needed. I knew exactly what I was getting into also so I had some cash set aside for such stuff. Don't be put off by mileage ....any car with 100K on the clock will need something.
Get yourself an Accel Aftermarket Warranty...$1400 for 2 years of coverage (for my car) and covers almost everything that goes bad on these models...like t-chain, radiator, A/C blower and evaporator, tranny etc, ball joints, self-levelling system. I'm guessing by 150,000 miles the car will need nothing for another 150,000 miles...except the oil changes and regular tune-ups....knock on burl.
