Generally, the seller pays the buyer's agent. Here's how it often works:
The seller signs a listing agreement with the listing agent. The seller agrees to pay x% commission to the listing agent if the house is sold. The listing agreement also will identify what happens to that commission if there's another agent (a buyer's agent) involved. Hypothetically, because it's fully negotiable, the seller might agree to pay the listing agent 6%. That 6% would be split--3% to the listing agent and 3% to the buyer's agent--if a buyer's agent is involved.
That's the way it often works.
But, because it's all negotiable, maybe the seller says that the buyer's agent will receive more (or less). You'll sometimes see an incentive, such as a 1% bonus, to the buyer's agent to encourage buyer's agents to bring potential buyers past the house. Sometimes the listing agent is willing to take less, so the commission might be 5%, with 3% to the buyer's agent. Sometimes--particularly with FSBOs (for sale by owner)--the seller is willing to pay a buyer's agent 2%-3%. Sometimes FSBOs absolutely refuse to pay any commission. That's their right. So an agent might show you a FSBO property, but might expect for you to pay the commission. The listing agent should make this crystal clear up-front.
So there are plenty of ways it can work out. But, bottom line: Usually you don't "neet to cough up some MORE money" to pay your agent. But to determine that, get your own agent--and that's a wise move--and discuss that with him/her at the beginning. You absolutely do not want to deal directly with the seller's agent. (Understand, in many states it's legal and done property is entirely ethical on the part of the agent. But to best represent your interests, you really need your own agent.)
Hope that helps.