Need to knows about older x series

Hello, I'm looking at buying a different car now that I'm in colorado and one of cars I've looking at are BMW x series. Mainly x5s and x6s in-between 2012-2016 and most likely over 100k miles. I understand bows can be pricey to upkeep especially after 100k miles but I also know theyre solid cars if you can maintain them so Im curious as to what I should be expecting if I did go down that route.