I will further clarify on the Buyer Agent are free statement as while that holds often, it is not a given (wrote about the same time as Bryan's, so want to further clarify as he is correct, but often, the Buyer does not pay anything using an agent for a successful purchase). So, further clarification.
If you do hire an agent, they will typically have a certain success % fee (let's say 3% for the sake of the discussion).
So, yes, Buyers agents are not free as upfront you sign a contract where you agree to pay a Buyers agent.
BUT, for the most part in a traditional sale where you are dealing with a home that is listed by another agent, the Seller is offering to pay a certain % to agent that brings a Buyer.
There are some exceptions of course:
1) Dealing with Sellers who are listing the property themselves and may/may not be working with agents.
2) Dealing with Banks- never quite sure what they might be offering either agent.
3) dealing with a Seller that is offering a % to the Buyers agent that is less than what you agreed to pay your Buyers Agent.
*I assume there are a few more that I am not thinking about on a Sunday morning :-)
Let's say you sign a contract with an agent to pay them 3% of the purchase price of a successful transaction. Typically, the contract has a provision where the agent is instructed to 1st try to get the 3% fee from the Seller or listing company. Where you can end up paying for the Buyers agent is if the Seller/listing company is only offering say 2%. Therefore, per the contract you signed with the Buyers agent, you are responsible for the final 1% at time of closing.
If using a Buyers Agent, make sure you ask if his/her % is fully covered by the Seller/Listing Company on the property that you are interested in. If not, you would be responsible for the balance if the property closes and you may want to factor that into your initial offer.
Also, if you do sign with a Buyers agent but you would like to go solo on any FSBO's that you personally find, make sure that is spelled out in the contract.