subframe and vanos are common issues, but a good service history and check will show any issues.
rust on arches - replace with new
noisy window cables/runners - replace with new/second hand
steering rack wear - replace
steering column knuckle bush sloppy - replace
final stage resistor making the heater not work correctly - replace (circa £50 if you have tiny hands)
ensure an inspection 2 has been done recently - it's bloody expensive
flat batteries in remotes - replace at £100, get battery changed £25 independant
*smg2 - pumps can fail (£800 been thrown about a lot)
*manual - sticking linkages, £50 in parts ish and box out to sort.
warped brakes, not very common, but £500 to replace fronts to a reasonable standard.
just a small list and some are common across the range of e46's.