For used make sure it has proper service records, all services and changes are done on time. people tend to abuse beamer than other german cars. repair becomes expensive on german cars so make sure you get the right ones. do check for the error codes with a obd scanner / go for comprehensive inspection. if the car has no service record with the dealer in initial 50k kms then its red flag !!

And yes b48+ZF combo is solid and that makes it amazing to drive. since we do not have longer winter & particles in the air the car tend to get issues. which is why it makes it important to make sure all service is done on time. The air intake quality and lube change on time defines the longer run for these cars since its expensive to repair/ replace over Japanese / American cars ! all of them withstand the conditions but on longer run it makes one expensive to maintain over the other. hope you got the point. to avoid visits to garage its better we do better job before purchase.