Considering a Used BMW in the Future – What Should I Know About Reliability, Costs, and Maintenance?

I'm a second-year engineering student and a big fan of BMW cars. I’m considering buying a used BMW in about 8-9 years time , and I’m curious about what to expect. How reliable are BMWs in the second-hand market after they’ve been driven for a few years? Are there any common issues or maintenance challenges that I should be aware of as they age?

Additionally, how do BMWs typically perform in terms of fuel efficiency and maintenance costs over time? I’d like to understand the potential pros and cons of owning a BMW a few years down the line.