I was reading a post on fb recently by a friend of mine who has been training dogs, cats and wild animals for movies and commericials for over 25 years. He said that many of the dogs used in his industry (including his dogs) have come from shelters and rescue groups.
60's dog star "Old Yeller" was bought for 3 dollars from a shelter; his real name was Spike." ... and Disney's original "Shaggy Dog" was bought for 2 dollars at a local dog pound."
So, spend some time at your local shelter ... you just may get a chance to scratch a future movie star behind the ears!!!
Here is one of my favorite videos. It features Joel's dog Duke, (one of his shelter dogs) in a Nessan car commerical (driving the car). You may also recognize Duke from the "Animal Planet" show called "Good Dog U"
https://www.youtube.com/watch?v=1XCKSXvhbQU