How much money does an English professor earn?

It really depends upon the school and the professor's ranking. As an adjunct professor in New York colleges, I earn 1200-1600 per course at a rate of 1-2 courses per term, so I can gross about 10-12K per year, not enough to live on. Nationwide, a full-time professor at an entry level rank will earn in the high 20's to low 40's. The highest-paid professors will make 60-100K late in their careers, plus whatever they earn from publishing, lecturing, and other side projects. It's a tough gig these days. Be careful of getting exploited. Don't work for hourly money at a diploma mill if you can avoid it!