Breaking into the Editing niche

[#1]

Hey guys,

I recently started working as a freelance proofreader and editor and was wondering if anyone might have suggestions on what to add to my portfolio. I know some samples will increase my chances of being chosen for a job, but I'm not quite sure about where to develop some or if I should try pitching at the lowest rate possible (close to free work) so that I might have some examples to show-case.  

Any advice or tips will be much appreciated -- thank you guys.

--Ricky