What else should be considered?
To start with, you should consider whether you meet the formal prerequisites for a doctoral degree and what routes are open to you. You can then start to think about possible dissertation topics and find an academic supervisor.
You should certainly find out as much as possible in advance about how the doctoral process works within your faculty. It is a good idea to study the doctoral regulations carefully. Among other things, this will explain the prerequisites for admission to a doctoral programme and the work to be carried out to obtain a doctoral degree. Many universities now also offer individual consultations to help you decide whether a doctorate is for you.
The amount of work and time involved in a doctoral degree makes it essential to consider the subject of finance well in advance.