I can't find any way to like "create a guest account" to access my account without just giving him my account credentials. How should this be done? I can't find any help articles on it.
If you can't get a second login and you don't want to give out yours (which is understandable), get the developer to create your site on their own server. When it is done and you sign off on it, you then transfer it to your server via FTP.
If there is a database, also get a SQL file to upload into the database