Recently EOS Name Service released the Beta version of their Marketplace platform. Users can now buy and sell names with EOS, while the auction and the Buy-It-Now features will soon be added.
Selling EOS Account names is actually a serious thing to do on the EOS main net, therefore be sure to read their Terms & Conditions and follow their User Guide at https://medium.com/@cypherglass/eos-name-service-marketplace-user-guide-37c209a149bf
Start using EOS Name Service Marketplace at: https://marketplace.eosnameservice.io