As far as I know, most PhDs from B School become professors. Some of them may go to consulting/Investment areas. It is really a hard road because it is hard to publish papers and apply the theories in the real world. However, the financial prospect is really attractive.

I know a few Accounting/Finance PhDs and actually their research is not that different with research in other fields. Most of the time you are reading papers, thinking about new theories, sourcing data and doing statistical analysis. Usually if you are admitted, you will have financial support. Therefore, admission is highly competitive. As I know, most B schools only admit 2-3 PhD students in Finance/Accounting each year.