What's the advantage of having an agent?
So far, the advantage for me is that my agent is an amazing developmental and line editor. I have two books in various stages of editing. The first one -- the one that hooked my agent -- has been my "learning" book, I suppose, the one where my agent points out every single flaw in everything from structure right down to how I use articles. She's not at all like what many people say about agents. She's not in it for the quick buck, or only to sell, though that's the ultimate goal. She's an ex-house editor who expects excellence, and she's extremely patient and supportive. Right from the beginning, we both knew me and my book have a lot of potential, but it'll take a ton of work to gain the skills I need to make the book what it could be. Obviously she thinks it's worth it or she wouldn't have read it multiple times, with multiple meetings and many many long editorial emails. In the end, a book has to be sold to justify all this work, but at the moment, the focus is on getting the book the best it can be. She has some successful authors on her list, and I think I'm benefiting from that. She can carry a new author who needs more guidance and doesn't pay off right away.
Anybody who wants an agent should know that the process is likely to run slower, maybe a lot slower, than expected. It's the nature of the trad pub business. Most of the time, I don't mind this. If I was older, I probably would. So it's really up to how you as an author like to work, and how patient you are, and how willing you are to listen to very tough -- and sometimes heartbreaking! -- constructive criticism. I'm willing to do all this because I suppose I'm a craftswoman at heart. I want to be a better writer, and I see how my skills have taken a huge leap forward under my agent. The financial stuff matters too, though, and of course I hope all this hard work will pay off down the road. But for now, I'm enjoying (and tearing my hair out over) this free education I'm getting in the craft and the business.