Litigation Hold for Company Shutting down

[mike_ironlogix]

We have a customer that is shutting down their business.  They need to put a litigation hold against both their exchange mailboxes for all users and everything in SharePoint. 

They have expressed a desire to reduce licensing cost as much as possible as all end users will be terminating employment.  What is the minimum licensing requirement to accomplish this?  Do we need to continue have each account licensed or can we accomplish this by having just the admin account with the appropriate license to apply enterprise wide?

[#2]

For Exchange data, you can get by for free thanks to inactive mailboxes: https://docs.microsoft.com/en-us/microsoft-365/compliance/inactive-mailboxes-in-office-365?view=o365...
As long as you have qualifying license before turning the mailbox into inactive, and at least 1 license remaining so that the service is not deprovisioned, no ongoing license costs will apply.
For other workloads, no free meals and you have to comply with the licensing requirements as outlined here: https://docs.microsoft.com/en-us/office365/servicedescriptions/microsoft-365-service-descriptions/mi...