Thoughts on this E61 530i?

[Antallica 15]

Quite keen on this low kms 530i, only 55k on it.

https://www.trademe.co.nz/a/motors/cars/bmw/530i/listing/4173323570

[Vass 830]

My mate picked one up for fairly cheap a bit over a year ago, also an early 2005 model. His first ever BMW and has been cursing it ever since. In the time he's had it, in addition to working on it himself, he's had it in at BM Workshop nearly every month for stuff he couldn't figure out and has spent multiples of what he originally paid for it in repairs. Vanos issues, some electronic airflow flap (not sure what it is on the N52, looked like an equivalent of a DISA flap from an M54) had completely fallen apart, constant check engine lights for emissions codes, airbag lights and annoying me chimes, sunroof leaking and so on. To top it off the fuel pump gave up one day and left him stranded. His did have around 120-130k km's but with age I think they'll all start having issues regardless of km's.

Another mate with a 525i started having issues with the rear air suspension leaking and the compressor giving out as well. 

You'll definitely have a better time of it if you're hands on but replacement parts are noticeably more expensive than the older counterparts and the added complexity doesn't help either. 

[Eagle 1662]

They are cheap for a reason. Along with the E65 they are a big step up in complexity and expense compared to the previous generation E39 & E38. Id wager low k examples (mainly imports) are generally worse because they are likely still using most of the original factory fitted parts, you also dont know what conditions that mileage was done under either. Mileage aside you have budget in repairs because they are all older cars now and very few people spend money on maintaining them properly due to cost etc. Service\maintenance history trumps all.   

[mzhu031 38]

Are they very different to a e90 in terms of design architecture and reliability?