if you are truly paying for a points rental from an owner, there are no additional fees for the stay. (there is an exception as aulani in hawaii does charge an extra fee to whomever is staying in the villa. aulani is unique, though.)
as noted, if someone is trying to rent an RCI exchange (which is a violation of RCI policy if RCI chooses to enforce it), there is an additional $95 fee for those stays.