Hopefully the M3 has better calipers, the standard E90 has crappy ones that go at about 8-10 years or 80,000 miles. Hopefully the rack doesn't go, that's a 4k plus job. Bilsteins may leak at 100k......not to mention other electronics.
The major problem with the E90/92 M3 is the rod bearings. Tolerances from the factory were a little on the tight side.
It’s known to be quite solid. Although there’s two areas; 1. connecting rod bearings, they wear and need a larger tolerance replacement at around 60K - 2. Throttle actuators (2 of them), plastic gears wear.
Outside that, especially once those are taken care of, people say it’s a solid car. But just like all German cars, make sure you maintain them properly!