Seeking well loved, unwanted, and cheap/free climbing shoes of various sizes.  I recently started teaching the basics of climbing for my son's boy scout troop (Sacramento area).  After watching them struggle climbing in street shoes I realized I need a cache of "loaner shoes."  I don't want to spend a mint on new shoes for noobs, thought I'd start here and ask around.  Thanks for any gear you can spare or leads on cheap shoes.  (Willing to barter belay duty or drive to local crags in return (on my "off" weekends).)