I think it’s important to realize that the job of every priest is to offer the sacrifice of the Mass, and to forgive sins. These are their primary functions, which they are entrusted with at their ordination. This is the essence of the vocation of priesthood.
That being said, not every priest will be assigned at a church, and say Mass once a day, twice on Sundays. I believe your friends is speaking about
missionaries, who go out and work for the conversion of other peoples. Missionary priests still say Mass, sometimes at the same location, sometimes at different places, depending on the circumstance.
Your friend should look at religious orders if he wants to do this. The two that come to mind for missionary activities for me are the
Maryknoll Fathers and Brothers, who work primarily in Africa, Asia, and Latin America; and also the
Glenmary Home Missioners, who are priests that serve the non-Catholic areas of the US. Many other orders have missionary activity, but these are two that come to mind.