well if you have a finished book, it really helps to get an agent. They just know a lot more about the industry. Some publishers require agents. To get an agent you need to send a query letter in. This website really helps with that: http://queryshark.blogspot.com/ Depending on your length, how well it's written and the contracts you use money varies.
You have to find an agent first (you'll need to write a query letter, google it if ou don't know what it is). Umm...i think they will find you the publisher, and then comes the money and everything. I'm not published, so I am not completely sure, but I hope i helped anyway...