What is there to consider when buying it second hand?
Generally there is not much to note. Do a normal test drive and pay attention to whether something stands out to you, just the normal stuff you would check when driving a used car. There are no parts which could have worn out already. The brake pads last well over 200,000km and the brake discs even much longer. Thanks to the electric motor and its 1-speed gearbox, the suspension is only beeind stressed in the ICE version of the smart car.
Smart cars with 35 kW and 55 kW are identical. The 35 kW are the constant power and the 55 kW are the peak power. Ontly the rare smart BRABUS electric drive have actually got more power. More about the tuning a smart car can be found in the blog unter the tuning tag.
Please never buy a smart ED3 that drove less than 5.000 Miles a year. The battery isn't mande for beeing stored over a long time and the range will decrease after 1-2 years, when you start using it normally again.