Anyone who’s editing data would indeed need a WP login, with username and password. Otherwise you’re risking just anyone coming along and editing the information.
One approach would be to create a custom role that can edit only their own listing – by this I mean, they can only edit the particular “listing” CPT that they are the author of, and no others. Then make sure that you create enough WP users to handle everything – you can use the gmail trick for this, which is, use your 1 gmail address and add a + symbol plus text. So if you have [email protected], you can also use [email protected] and that will be a unique email for WP that also sends all its messages to your [email protected] account. When you import the data, make sure to assign separate authors to each business. And then once you have real business owners to edit the data, just update their accounts to their own emails and let them choose their passwords. Because you’ve set up a custom role, they’ll only be able to edit their own business and not anything else.