Best to use a OBD code reader to see what errors are present in the car's computer. Although this information won't give you a definitive answer, it will narrow down the problem areas.

Base on the limited information, it 'sounds like' it may be related to the ABS/DSC module, one of the rotational speed sensors, corrupted or defective Body Control Module (sub computer), or electrical connectivity issues...  Too difficult to say without seeing the car...

So, I have the opportunity to get a 2009 mini JCW at an amazing deal. My question is it has several warning lights including ABS issues. Brake light is constantly displayed. It is stuck is sport mode or light mode? not real sure. I have never owned one of these but have always wanted one. Does this seem like a major issue to fix? Maybe the DSC module? Wheel speed or brake sensor?