Purchase advice 6-series BMW

Hey, what a budget I have to expect if I want to get a good used 6 Series BMW (somehow that sounds so cliche moderate…) Was more Mercedes driver with the E class, but the 6 was always a beauty that got me under its spell. Budget would be about 15-18000 € would like a pleasant color if outside black zb inside bright, or outside bright inside dark. Automatic, clearly not running too much (i.e. over 160,000km) whereby I also don’t know how well the engines in the KM collect and when they slowly give up their mind on average. Automatic motorization no matter (lovingly lower) gasoline or diesel exterior mirror electronically fold off still Keyless Go or Start button where are the differences in the facelift ?