you have seven days to pay your tier and then you are blocked from logging in. After that, you have no access to any lindens and must pay your delinquency via credit card or other form of outside payment. If you remain delinquent after 30 days, your region/land is reclaimed and your account remains blocked.
You can pay your delinquency 30, 60, 120, whatever days and your account will be restored, but your land will be gone. If it was a full region, it will have been shut off and any objects that were on there will have been lost. They are not returned.
An account is never truly deleted, but often the inventory is purged after a period of time.