I just completed an M.A. thesis in English literature, and I mean just. I tend to be light on the number of sources I use and I like to have favored sources and work it to exhaustion.
My thesis is about 30,000 words, about 50 percent more than the minimum at my institution. I have 27 secondary sources and six primary sources. The institution requires 20 sources, I don't if that's 20 secondary or 20 total, but what I did will give you and idea what you need to do.
I'm not just out college. In fact, I am senior citizen age. My writing ability is equal to that the people who write the journal article and equal to that of a professional historian too. Reading the journal articles I have had to read to do my seminar papers and my thesis, I have seen many that are excessively heavy on sources. Some are light on sources but seem nevertheless to be good articles.
How you primary sources you cite might depend on your topic. It could be only one. Conceivably, it could be none. For a master's thesis in literature, the minimum might be one secondary source for each thousand word. In imagine, in that case, that it might be double than many for a doctoral disseration. In that case, the number secondary sources for doctoral thesis would have to be around 150.
How many source might depend on the individual and how that persons works their sources. But I would still say, expect to be required to have 150 sources or close to it.
My thesis was low on sources in part because I first outlined a theory and then applied that theory to the characters of four novels without much reference to outside sources.