you will not find a 'kill' pen in Ca. No one is going to say that is the kill pen. Look for feed lots in the phone book or on line. Cruise past them, if you see horses in the hold pens, go Politely talk to them. Don't say kill pen, don't say slaughter .
Just ask if they are selling the horses. Don't expect to get them for free or to cheap. Mikes Auction and Tulare Auction have cheap horses, go to the tracks, talk to the stable hands, give out fliers that you will buy the unwanted race horses, I think they are going for about a grand per horse (TB) right off the track. Look for Dispersal sales. Go look on Craiglist, right now there is a bunch for sale in the Inyo Kern area..