Roof motors aren't that bad if you keep the drains clear.
If your planning using yours as a DD and kept outside there are 2-3 options of having the motor relocated into the boot.
Welcome aboard. If your coming from an M3, you probably have a good idea what to check service & condition wise. The E85/6 Zed4 is turning out to be a solid reliable sports car. The rear spring fail, but cheapish to sort. The VANOS even works There are a few horror stories but they are indeed few. Are you looking at E85/6 or E89?
take an obd scanner when ur looking at cars. i'm paying the price now for only taking a basic scanner.
#Hopefully will get things sorted but would have maybe swayed me away from the car i bought.