I read this book in '93. I have been looking for it for ages now. I remember a young man living in the modern world and I believe he jumps a fence and is in a magical world. all of a sudden he is introduced to an old hag/witch who is going to teach the man magic. The teaching is tough and he is put through hell. I wish I knew more, I just know like some Terry Brooks books, it was a great read and would love to read it again. I know that the book cover was quite similar to Terry Brooks. Thanks for anything you can help with.
It's far from a perfect match, but could it be Greg Bear's The Infinity Concerto (published in 1984)? The protagonist starts in the modern world and enters a magical one (though not by jumping a fence, I don't think), and is taught magic by a trio of old hags, which required some fairly harsh methods.
From Wikipedia's summary:
The book's present story follows the experiences of a young man named Michael Perrin, a would be poet ... Following the instructions on a piece of paper he found inserted in the book, Perrin enters Clarkham's house, which has been vacant for decades, and soon finds himself in Sidhedark, a world inhabited by a powerful race of beings calling themselves the Sidhe ... She orders him to go see the Crane Women, who are a trio of "Breeds" (part human, part Sidhe), who live on the outskirts of another town populated by other Breeds called Halftown. They train him with exercises that seem pointless and incomprehensible.
Here's the book cover I'm familiar with: