If you use modern hosting, you can find the function of selling your domain on the hosting. Personally I use https://mangomattermedia.com/ and when I finish working on a project, I sell it, that's my job. If you've unfinished projects and you want to sell them, you can contact me in the PM, perhaps I'll buy your project and domain from you. This is a very profitable business, I would advise you to try it. Be careful when selling because there're a lot of scams on the Internet that can deceive you.
