They vary from state to state, and town to town. In Massachusetts, for example, there is a cost to the seller to record the new deed. It's equal to $4.59 per $1000 of selling price. So if the home sold for $100,000 the cost would be $459. etc.
There are also fees to discharge their current mortgage(s), as well as preparation of the deed that is provided to the new buyer ($150+/-)
Then there are legal fees for the seller to have the purchase & sale agreement negotiated with the buyer's lawyer. (The escrow process is different in Massachusetts than most other states).
Prior to selling your home in Massachusetts you must pay to have your local fire department confirm that your smoke detectors and carbon monoxide detectors are all working properly. That's about $35.
And if you have a septic system, instead of public sewer you have to provide a document that the septic system is working properly. That document, referred to as a "Title V" document is completed after a certified septic inspector checks your system out. That check out will cost you around $400., again, depending on where you are located.
Beyond that (and a Realtor fee, if you hired one) you could, as an owner, agree to pay some/all of the buyer's closing costs if that were agreeable to both parties. It is rare, but, let's say you really wanted to sell your home, and you hadn't gotten any offers, and then one FINALLY came along, but they wanted you to pay their fees, well, you might just be willing to do that... just to be able to move on to the next phase of your life. But it would not be required costs, as the other ones would.