I agree with the Freecycle approach (tangible items that are free) with participation open to Members with a certain number posts (100?). I'm also thinking that a "Wanted to borrow" category allowance might be of interest. For instance, I have seat belts. As we drive only a few times a year, they sit idle the rest of the time. Another member might welcome an opportunity to "test-drive"
different models of seat belts before making a purchase.
One thing to keep in mind though is that in allowing any used goods to be posted there is the potential of liability for pets.ca and the member posting the item. This will require global "CYA" disclaimers to be written by legal-beagles and that will require $.