Creating a member login that allows users to post information to front facing site

I am putting together a proposal for a client and trying to determine if Squarespace has the functionality or ability to integrate with a 3rd party platform to meet the needs of a website feature.

The client specializes in tourism. They have a functionality on their current website that allows local businesses to login and post listings of last minute availability they have for tours, lodging, etc. Since this content is managed by the business itself, I was thinking of creating a member area where businesses could login and post content that is then reflected to the "public" side of the website. However, it seems like member areas only allow access to content posted by the website owner.

Is there any way to go about this with member areas, or a recommended integration I could use to create such a feature?

Thanks!