Your mention of the tools being 'too difficult' for a lone developer is the exact reason I suggested mercurial. With SVN you are essentially setting up a faux server on your USB stick (or where ever), configuring it for the project, checking it out and working on it from there. With mercurial you just enter a directory of existing code, initiate your repository right there, add your files and BAM your code and version control are all in the same directory, no other server needed. Having the ability to essentially place any directory under version control in place with no external server configuration makes it cheap to do so.
Heck, I've never tried it, but with mercurial you could take each job directory that contains all your binary files (AutoCAD drawings, word documents, excel documents, etc.) and place it under version control as mercurial can certainly do binary files. This would allow you at minimum get a snapshot of states as files were transmitted to customers, etc. Kind of a poor mans document management system.
