Dude, you are thinking of buying a 7 series / s class level car. Expect it to cost money and be expensive... Basically after about the first year, the cost is linear for the next few years. You don't really save much money buying preowned vs. buying new due to that kind of linear curve and also maintenance and repairs... Buying a 4 year-old car today, depending on mileage may require you to do a full brake job in the next 2 years. Also there will be other wear and tear items to replace.
As new gen battery will be released this year, just think about it. In 2 more years, a 6 year old car with no AP, original seats, 80-100k miles... won't be worth much... Really shouldn't be worth any more than a 6 year old 7 series with that many miles, which isn't much. However still costs the same to maintain and repair (and with Tesla you can't fix it anywhere else).