I would ask them if they knew about all the healt issues, and if they have any idea of how many tjiongs that can go wrong with the bitch/puppies when it´s time to deliver the litter.
Here in Sweden we say that you must have a buffert of atleast
10-15 000:- Swedish Krones (1200-2000 USD) just to pay for everything that can happens, like ultrasound, x-ray, c-section( spelling???) puppies got stuck, what you have to feed them during their 2-8 weeks of age, what you need to give to the bitch during the months before the puppies are born etc etc.

When I talk to a bitch owner who is looking for a stud dog, I bring up all the bad things, as well as the positive. If the bitch is dreadful looking or have a completely disgusting pedigree, I press on the bad things.

I also recommend them to buy the books they can find about whelping, breeding, feeding etc.