There are still a handful of legitimate publishing companies that accept unagented novels, but let’s be frank: Having an agent represent you and your novel is the single best way to break into traditional (or “legacy”) publishing.
Let’s clarify a few more things to figure out where you need to start. Click the sentence that best describes you.
I am working on a novel but it is not yet complete. (Choose this whether you have written one page or 500, but that the novel is not yet completed.)
What do you mean by “legitimate”?
Legitimate publishing companies and legitimate agents do not charge the author fees of any kind. The only exception I am aware of is paying (very low) shipping fees for some sub-agents, like those dealing in foreign language or film rights. Apart from that, legit publishers pay you. Legit agents do not get paid until you do.
Any company that you pay to publish or represent you is either a vanity press or very possibly running some kind of scam. Do not confuse that with choosing to pay a company like Lightning Source or a print-on-deman (POD) company to print copies of your novel which you can then sell yourself.