I am happy you have a strong intention to be a monk.
Still, life does not happen the way we want it to most of the time. Five (fifteen?!) years is a long time. Everything changes. The mind is fickle. Your mother could die. You could die. We usually think we are preparing for something, some time better in the future, but really, there is no better moment than right now. This is the end. This is it.
Have you ever been on retreats? Long retreats? The lives of many monks, if they are dedicated, are like lifelong retreats (with periods of less intensive meditation, and more work and/or study). Are you sure you are prepared to relinquish all sensual pleasures, keep your eyes downcast most of the day, give up all your hopes and dreams of becoming somebody special, and let go of most, if not all of your hobbies? It sounds like there are still worldly aims in the mind that could hinder one's practice as a monk. Being a monk is not about becoming somebody great. It's about being an ordinary nobody and striving for liberation from craving.
Not having your mother's permission is a valid reason not to ordain. Not having a penny to your name is a rather poor excuse not to ordain. How much is the ordination ceremony?
It takes a mature person to be a monk. If you feel you are mature enough, great. Go for it. If romantic, idealistic thoughts of a monk's life are predominant in the mind, it might be better to practice in daily life and go on a few longer retreats to get a feel for a renunciate's life first.
All the best to you, friend.
Do Good, Avoid Evil, Purify the Mind.