Welcome aboard!
The Owner who chooses to rent sets their own cancellation policy. Typically (but not always) it is a no cancellation policy.
This is because the points used to make your reservation may have been borrowed or banked, or will expire before a 'replacement' reservation may be set up (or there may be no other dates available, for example this December is fully sold out), or if you cancel less than 31 days prior to your trip, the
DVC points become holding points, which are severely limited in use and thus value. Or, if you shorten your vacation, or cancel the day of arrival, the points are forfeit. These are DVC's rules, the Owner has no options here.
Renting is not for everyone, for a good discount you give up flexability, and control.
I would suggest you get a written contract from your Owner.
Even though there are risks to you (and the Owner as well) in renting, there are no horror stories of ripped off renters that I can find here on the DIS.
Good luck with your vacation planning!
-Tony
P.S. You can buy
trip insurance to cover those unplanned emergencies!