I think it depends on how you're going about it and what genre you're writing in. For book-length pieces, if you are writing non-fiction or literary fiction, the protocol is to get an agent, not submit to publishing houses directly. If you're writing science fiction or fantasy novels, publishers often take manuscripts directly from writers.
But if you're writing short stories, you can just submit those directly to magazines. All in all, it often takes months to get a response, and often longer to get an acceptance.
Some people do pretty well with self-publishing, which bypasses all that. But then the hard part is not getting your work accepted but marketing yourself and trying to get sales through word of mouth and reviews.
Keep at it is all I can say, and good luck!