When a customer calls in to cancel their contract they lose access to their files. Access via the Vertex application is what the contract provides.
Vertex does provide copies of the databases, if requested, but retrieving useful information requires technical assistance from someone with the necessary skills.
The customer’s instance can be archived and made available upon request for a minimum monthly fee plus a charge each time it is reloaded. Cost is by quote as it depends upon the modules the customer is using.