Just want to add -- some scam agents are even sneakier than the ones who ask for upfront fees. They'll insist you need "professional editing" and "recommend" a certain independent editor, when really, they just get paid by the so-called editor to send writers there. Other scam agents might send you to a pay-to-play publisher with the same results. Some companies even claim that can help you write a query and find an agent for a hefty fee. Again, almost across the board, it's a ripoff.
Unless you have no knowledge of your market whatsoever, real agents have sold books you've heard of. Or at the very least, that you could easily find on the shelf of any local bookstore. Not all are open to submissions all the time, but when they are, they don't charge a fee. Ever.
Read Writer Beware and learn how the industry works. Otherwise you're a very easy target for scams. If you have an awesome book that people want to read, people will pay you, not the other way around. If some time down the road, you decide you'd prefer self-publishing, even that can be done for no upfront cost if you've got the willingness to learn.
Best of luck!