Should I expect to pay 10% of sale price in selling costs? We are using an agent.
Generally 3% commission to buyers agent and 3% to sellers agent (then a portion of that -usually half - goes to the broker they work for, etc). As AR said, they are negotiable, and ease of negotiation depends on your real estate market and various other factors. Around here (NW Washington), they general decrease to 2.5% per agent for properties over about $500k or $750k - I forget since I don't have anything that valuable... Generally the seller pays all commissions, while fees like advertising, photos, etc typically come out of the listing agent's pocket. Around here, if you stage the house, they might make you pay for that, but for more expensive houses, the agent may pay part/all of the cost of staging. Generally, the more commission they are looking at, the more the agents are willing to contribute toward marketing the house.
You can have your agent outline what else to expect in terms of costs. Excise taxes are location-dependent. Assuming your "-WA" in your name means Washington State, here is a
table of excise taxes for different communities in the state. That brings it up to 7.3-7.8% so far.
After that, there are all the various things AR referred to. Here in WA, closing is generally handled by an escrow/title company who charges an additional fee which is traditionally split between buyer and seller.
Whether or not you pay any concessions to the buyer in terms of their closing costs, repairs, etc is entirely up to you, but there is no standard assumption that you have to do so. Every home inspection will find something that needs to be fixed. My wife had one buyer that insisted the seller replace 2 burned out light bulbs... If they want repairs done (or their lender demands that they are done as a condition of the mortgage), you could pay yourself, split costs with the buyer, or just tell them "take it or leave it". It just depends on how strong a negotiating position you have and how badly you need to sell.