The default setup of Paid Memberships Pro configures all members as users with the default role (under Settings > General) and (selected) membership level. When a user cancels membership, the user’s subscriber account remains and will show up under the Users list in the WordPress Admin. The code recipe below will delete that user account upon cancellation.
When a recurring payment fails, the member and the admin are notified of this failure. Depending on your gateway, the user will receive a link to update payment information on the Billing Information page on your website or directly with the gateway (for offsite PayPal gateways).