I purchased a new Mac running Mac OS X v10.8.5 (Mountain Lion). I\'ve seen it written in various places that SVN is installed on OS X by default, but when I
Subversion itself is no longer included with OS X. It's now included as part of Xcode. So one option is to install Xcode and then install the Command Line Tools. If you're not going to install Xcode anyway then you may be better off downloading a different installation of Subversion. On top of that the Xcode version is usually fairly behind on releases now.
So I'd suggest getting it from one of the sources on the Subversion Projects Binaries Page.