Any PhD program worth attending will have funding, typically with an offer of research and/or teaching assistantship which gives a tuition waiver and a living expense stipend (but check that the stipend is sufficient for the area that the school is in).
The most obvious related jobs are English college faculty (highly competitive for a tenure-track job after earning a PhD) and English high school teacher (supply/demand varies; also needs whatever teaching credential is specified in the state/region).
Other jobs that English majors aim for tend to be the major-agnostic jobs where a bachelor’s degree is expected or required, but do not require specific majors.
In general (regardless of major), it is best to minimize undergraduate debt. Many would say no more than the federal direct loans ($5,500 first year, increasing slightly later years); some are more conservative than that and recommend no debt if you have such an option. Pre-med is actually a situation where minimizing undergraduate cost and debt is more important, since medical school is enormously expensive, most pre-meds do not get into any medical school, and the most common majors for pre-meds (biological sciences) do not have highly paid job prospects at the bachelor’s degree level.