John L. Flynn
Start small. So many writers want to write these lengthy, multi-book stories, and while ultimately that is where you want to go, you should start out with the short story. Most publishers won't read that lengthy, 12-book series that you've dreamed up, even if it is better than Game of Thrones, but they will read a shorter work. I always tell my students to write short stories, and to learn their craft writing small. Short stories from new writers have their place, and are likely to sell because there are a lot of venues for the short story. Build up your career as a short story writer, and then write your first novel. I think you'll find that writing the novel is going to be a lot easier. Most publishers won't read first novels from writers without a track record, but you build your track record with the short stories you've written. Agents, too, will seek you out if you are an established writer with a career of publications.