I didn't have a mentor when I started out writing more than twenty years ago, but I wish I had. This morning, I spent an hour or so with a young woman interested in writing for kids. She was sweet and enthusiastic, but very naive. Many seem to view the life of a writer in romantic terms when really, it's a lot of hard work. Being a writer requires commitment and tremendous self-discipline, generally, without much in the way of monetary compensation...Ideas are all well and good. I have hundreds of story ideas. But, a book is a whole other matter. It takes time to plan, time to write, and time to revise, and then revise again. Furthermore, books involve a skill set that can't be learned overnight, and takes a lifetime to master. If it were easy, a whole lot more people would be doing it.
As well, few young people are aware that writing is actually a business. No one wants to publish your book just because! It costs publishers money in editorial time, designing time, print costs, advertising costs, and the usual overhead. Publishers want, and need, to make money from their publishing line. They won't publish your book unless it can make them money.
I hope the young woman I spoke to takes the time to learn not only the craft of writing, but the business, since the two go hand in hand. Maybe one day I'll get an excited phone call telling me that her first book is coming out. I hope so.