Buying an adult pug , what to look for?

If the owner can give you up to date information on his vaccinations and health history and the dog is sociable and friendly then it's probably a safe buy. But, you shouldn't overpay for this dog. He's not worth more than $50, which is about what you would pay at a shelter. You are doing this person a favor by taking her in, they shouldn't be trying to profit from selling their dog.