I think this is not only a wonderful but very generous idea. Check out the details on CA Marshall's website.
(copied from her website)
It's that time again! Time for another FREE EDIT contest!
Just like previous contests, I'm giving away a FREE substantial edit! (That's plot, pacing, character development, etc, up to 100k words) to one lucky reader!
It's really easy to enter, just fill out the form linking to something specific you want for christmas, or something you'd give to your favorite writer or reader. ENTER ONCE PER DAY.
To get more than one entry per day, link to this contest. Fill out the form again every time you link or tweet, or whatever. Please include direct links, and if you post somewhere, the post must be about this contest only. Please don't spam your friends. One entry per type of post (one twitter status, one blog post, etc) per day. To fill out the form again, refresh the page.
For 10 bonus entries, post my button anywhere on your blog! If you include the button in your blog post, that post is worth 11 entries! If you use the button, make sure you note that the button is included when you fill out the form. The button and code can be found in my sidebar.
Contest is open worldwide (but has to be in English) as everything is done by email. I can wait up to a month for you to finish your MS if it isn't finished by contest end (midnight December 10th), SO GET WRITING!