My dog Lola is a Schnoodle, half mini Schnauzer and half mini Poodle. She is now known as a "Designer" dog and sold for upwards of 1500.00. While I will admit to being a bad example and buying her at a pet store, I did not spend anywhere near that much for her. More like 300.00 I think. She was a mutt when I got her and in my mind remains so but that's a good thing.
However, she is a good example of why not to buy from a pet store. She has had food allergies, chronic gastritis, many retained baby teeth, loose dew claws, fatty tumors and luxating patella's, better known as loose kneecaps.
I knew about the kneecaps from the beginning but was told they wouldn't be a problem, they were. She decided a cat needed to be caught and no baby gate could hold her. Her knee popped out and had to be surgically repaired.
Before the surgery she was good with other dogs but after she decided that she no longer wished to be jumped on or play that way with other dogs. Who could blame her? So I would just warn people off. Ask "is your dog a puppy?" and if they answer was yes, say "she isn't very nice to puppies". If they ignored me she would tell them off in her sternest voice. She has never drawn blood (maybe she would but I don't let it get that far) but she can get a bit fiercesome. It never fails to make me laugh a little because she is a raggedy little cutie but she can make a big lab say "Oops, so sorry ma'm. I didn't mean to make you mad" as he belly crawls away. How can one so small command such respect?
This went on until she met Hank, my roommates long-haired, Blue merle Chihuahua. He somehow penetrated her cold facade and made her play again. Mostly it consisted of wrestling and Hank chewing on her ears but I was glad to see it :)