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).
It depends on the journal, but it is normal for the peer review process to take a year or more (and much longer for top-ranked journals). So you should submit your first paper during your second year at the latest.
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 a coauthor (Year 2-3).
Conduct your own research topic that concludes your Ph.D. study (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.