To obtain the Ph.D., you should have three research papers, one of which should be published in refereed journals.
Here is the expected schedule:
Publish your master's thesis (Year 1).
Work as RA for one of my ongoing project to improve the coding skills (Year 1-3 or 1-2)
Work with me for one of my early-stage projects as coauthor (Year 1-2).
Propose a joint research project with me, and complete it (Year 2-3).
The prerequisites are
graduate-level econometrics and microeconomics,
perfect understanding of "selection bias",
strong knowledge on mathematics and statistics, and
strong skills in writing codes for data management and estimation.
Students are expected to obtain these skill and knowledge in our master's program and my regular meeting.
I require the same level of knowledge to all the applicants to our Ph.D. program (and actually I have rejected hundreds of applications due to the lack of these required knowledge), because otherwise it is super difficult to complete the Ph.D. thesis in three years.