I would be flexible as to the year and focus on the mileage,maintenance history and a 1-2 owner vehicle to go along with that PPI. As a safety measure I would strongly consider a warranty. At 100,000 you are into the range that some of the more expensive parts such as suspension components are coming to the end of their life cycle. An X5 with 75,000 miles or less would be a good target.

Just the other day I spent a couple hours in a shop that has been repairing ZF transmissions for many years. I was in the rebuild area with main tech. In his view the ZF5hp24 is a better overall transmission. He said the 6 speed has more problems but is still a good transmission. He mentioned that almost all 6 speeds that come in have the same problem which does not require a rebuild. I can't remember what part he was talking about or the cost to fix. I would have a transmission shop familiar with ZF transmissions do a separate PPI.

I have been changing transmission fluid every 40-50,000 miles since new and use ZF fluid. He said that is best practice. Very often fluid changes are because the transmission already has symptoms and fluid change is an attempt to fix it, that's too late and further developing symptoms in a the near future are attributed to the fluid change.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas