Anything old and BMW will be "unreliable". You can't buy one and expect to drive it without issues.
Having said that, if you buy one, do the cooling system, vacuum lines and anything specific to the chassis that needs doing within maybe a month then they will be reliable.
In my experience
Reliability
E36>E30/e34>E46
Cost of upkeep
E30/early e34>e34/E36>E46
Availability of parts
E36>E46>E30>e34
BMW
Aiden Taylor
James Diaz
>rust
not really though
Wyatt Rogers
>Which gen is the most reliable/least expensive to own?
The one still under factory warranty.
Asher Powell
Biggest issues on the e46 is sub frame cracking, and the cooling system.
Brayden Taylor
There's no such thing as a ReliablE German Vehicle.
Jeremiah Young
i just bought an e46. 2002 325i sports package specifically. in good condition, everything taken care of, 125k miles, things that needed fixing or replacement got it. did i do good?
Jonathan Cox
There's no such this as "unreliable BMW".
Just neglectful owners and slightly more stringent maintenance schedules.
Cameron Clark
This
Liam Watson
So much this
Josiah Garcia
E36 outside of the USDM are fine generally. The M50 engines are tanks. M52 isn't far behind but the VANOS seal has to be replaced fairly often. S50 is a bit more of a headache but what do you expect.
Main thing to look out for is rear subframe problems but it's fairly cheap to reinforce. Electrical issues is the other thing. They aren't a big deal on an E36 but there will probably be a handful of them. Easy to fix but annoying. Unlike later BMWs though an E36 will still run with half the electrics not working.
Besides the nikasil problem on the 328i you really just need to remember that they are 20-25 year old cars now. Also assume the VANOS seal is fucked if it's an M52.