SharePoint Teams

Hi Andrew,

Your requirement can be met by using Microsoft 365 Groups and Guest Access.

Here is a list of Microsoft 365 Group features:
A shared Outlook inbox
A shared calendar
A SharePoint document library
A Planner
A OneNote notebook
Power BI
Yammer (if the group was created from Yammer)
A Team (if the group was created from Teams)
Roadmap (if you have Project for the web)
Stream

Here are some resources that you might find useful:

Microsoft 365 Groups
https://support.microsoft.com/en-gb/office/learn-about-microsoft-365-groups-b565caa1-5c40-40ef-9915-60fdb2d97fa2

Guest Access
https://docs.microsoft.com/en-us/microsoft-365/admin/create-groups/manage-guest-access-in-groups?view=o365-worldwide

I hope that helps to get you started.