allocating disk space for shadow copy for share folder

Dear All,
In my place, I have windows 2003 server R2. I have share folder with
62 GB data.
I want to implement shadow copy, as sometimes users in my office need
to recover their data.
My questions are:

1. As I have 62 GB data on my server, how many disk space should be
allocated for shadow copy?
2. How long is the interval of shadow copy should be configured? twice
a week or twice in a day or ( have no idea the best practice for it)
3. What is the risk to implement this technology ?

Thanks in advance.
Your help is very appreciated.

Best Regards