What is the usual back-up policy? What kinds of backups are usually available?

Many Hosting companies do not offer redundant or mirrored backups but will occasionally run courtesy backups. However, any backups that are run are often in addition to the Terms of Service and are not usually guaranteed. Customers are normally encouraged to run periodic backups of their sites through the provided cPanel and store such backups off site or on their own computer.
You can create your own copies using SSH/Shell Access.