I am considering starting a service like what these people offer: 
http://backupmanager.com/Pricing.htm

I have the internet connection (I have a 4 Meg a sec connection that
allows me to host servers as I already do).
I have the servers UNIX (Solaris 9)

What are some software programs that I could use to deploy such a
service, I.e. a internet version of retrospect.
Cost and comparisions of products please.
Remember I would be selling this to the advarage user, so the client
software has to be easy to use and understand.
The server software must be compatiable with solaris for sparc.
Must support some level of encycrption for users security.
Must give the users some way to retrive files.

I am considering only allowing people to back-up their mydocuments
folder, but it would be to me automated i.e. sending me a updated copy
of there files every night.