If you’re a designer and planning to build other Webflow sites, get the Freelancer workspace plan, and all of your sites will have the full range of features during design, including custom code.
If this is a one-off project, and you’re planning to have the client host it in their own workspace, then yes you can set that up now, give them the password and then have them buy the site plan ( no workspace plan ).
However this is confusing, you might do a video to show them exactly what to do.