i have an e46 convertible, cracking car.
condition is vital for resale as is a fsh if you can get one.
thermostats fail, so heaters are shite.
window regulators fail, listen for twanging on their way out.
sub frames can crack on rear, from abuse usually.
rusty arches, noisy gearboxes, stiff out of fifth is a cheap fix, but more often box off to change the part.
remote batteries fail and costs about £20 for a cheap fix, or dealer territory for new keys.
warped disks tend to pop up a lot, heavy car remember.
just a few things i've come across in the last few months.