If you are a fixer mechanical guy, like to fixing and tinkering with cars, have a garage, or are buddies with someone who has a garage, have extra cash for a restoration project... Then Go For It! Otherwise, you may be signing up for an expensive project.
Definitely take it to a BMW Dealership for a pre-purchase inspection!
But on the other hand, If the car has been very well maintained, you have proof/service records, and you want a project it might be a fun one considering the car went for $100K in 2008 and you can get a good one for around $16k now. Also, the cost of a crate engine or rebuilding one the might be worth it if Everything else is in Excellent Condition!
Good Luck and let us know what you decide to do.
https://www.thecarconnection.com/ove..._6-series_2008
Not a lot of recalls...
https://www.cars.com/research/bmw-650-2008/recalls/
The top might be a problem...
https://www.gotaclassaction.com/bmw-...ible-vehicles/