Some writers have to their work completed and edited before submitting a query to an agent. But not all writers. Sound weird?
There are two main genres that define how a writer publishes their work in the traditional route: non-fiction and fiction.
Fiction queries are the kind of queries that everyone hears about. You finish your novel. Wait. Edit. Edit some more. Get a couple of beta readers. Edit some more. Sometimes even get a professional editor involved. Only after the writer has done everything they can do to make the story the best it can be, they submit a query to a literary agent.
(Note: The following does not generally apply to memoirs or creative non-fiction. Those books do still query.)
The non-fiction querying process starts before the book is even finished. Instead, those books are sold on a proposal.
A writer can submit a proposal to a literary agent or a small press. If the proposal interests them, they will support the writer. They keep in contact throughout the whole writing process and can help a little along the way. If there is any delays, there is no need to worry, but please do let the agent or publisher know.
Now, this process is more flexible than fiction writing. Some non-fiction writers do wait until their project is complete before querying, but that’s not the only way to do it. Since non-fiction is sometimes overdone, it’s easier to send a proposal and get feedback rather than to write a book to then realize that there are too many books covering World War II in that same exact way already.
Hope this helps in some way! If you have any questions, leave a comment down below!