Building on what was said previously (/give namechange), and you have to agree on a price beforehand (You can find buyers at
viewtopic.php?f=15&t=65098), however It's recommended to also take SSs of everything (giving the namechange and receiving the cash, just in case someone tries to scam/fake report you).
No, there is no command that trades a namechange for a certain ammount of money automatically with other players. You can however sell it in the UCP for 1 million (
https://sa-mp.im/profile/sellnc)