what is the URL of a "users" personal web space on a RaQ4r? what is the FTP host name?

The url of the users is http://yourdomain.com/users/yourname

the ftp hostname depends on your dns configuration.
Generally login with yourdomain.com.

if a user who does not have admin privlages logs in via ftp will he be placed directly into his user account directory or will he placed somewhere else?

http://www.yourodmain.com/~username as well.

If he doesnt have admin rights he will see one directory on login which is /web he cant backup any further than that.