It would probably help to get a Masters in Theology if you wanted to pursue it as a full-time career. Some people are naturally gifted in studying Scripture and/or theology, and so they might be able to forgo the formal education and carve a niche for themselves as freelance speakers and writers. But a lot of things have to line up to go that route, IMO. Having an interesting conversion story helps.
When conceiving of potential jobs in service of the Church, I tend to first look at potential employers. There are parishes, Catholic elementary and secondary schools, diocesan chancery buildings, Catholic universities, Catholic non-profit apostolates (like Catholic Answers), Catholic publishing companies, national Catholic associations, Catholic hospitals, etc., etc.
From there, you can figure out the types of positions that would be available. Take a Catholic school. Within a school, there is more than just teachers. There is administrative staff, library staff, maintenance staff, development staff, alumni relations, etc., etc. And each of those positions carries with it its own set of qualifications a potential candidate would need.
Or take a Catholic publisher. They need sales representatives, editorial staff, secretarial staff, marketing staff, design staff, IT people, etc., etc.
If a person is serious about serving the Church full-time, they need to pray earnestly about where their gifts are and where God might be calling them to serve. When they have an idea of where their niche might be, then they need to research it and find out what places hire people like that and exactly what qualifications they need in order to be a qualified candidate for such positions. A person needs to be willing to do the leg work, and even potentially get some training (perhaps even involving going back to school). If that seems like too much work to bother with, then I would question why they want to work in service of the Church at all.