The commission you pay will most likely be a percentage of the sale price of the home. Neither law nor industry standard sets the commission schedule, regardless of what the agent tells you is typical. Remember that commissions are always negotiable, and whatever the commission is, make sure you agree on it before you sign the agency listing contract.
SUGGESTION: If you will be using the same agency to sell your home and buy another, push for a break on the selling commission. If an agent knows he or she will be making two commissions as a result of your move, they should be willing to shave a point or two off your selling listing.