You cannot switch between being a Client and a Vendor once you’ve selected either option.
Once you’ve chosen to set up as a Client or a Vendor, you can create a new business of the other type by pressing your name or avatar in the upper right corner and then clicking + add a new business in your user profile.
Click here to learn more about what it means to be a Client on Liquid.
Click here to learn more about what it means to be a Vendor on Liquid.