Ah... this is a serious question and one that takes a lot of discussion.
Firstly, its as Michael says you can never predict the future - I've met people who've bought puppies from the newspaper or a neighbour, usually mixed breeds, and who have had strong healthy dogs which lived long full lives. I've met people who've bought purebred puppies who've had heartache all their lives or lost them early. I've met people who bought BYB or pet shop pups who've had heartache and people who bought purebred dogs who lived long healthy lives.
There is no guarantee.
No one can guarantee your puppy will be healthy and live a long life. Not the vet, not the breeder. I personally dont believe in guarantees. When you have a child no one can guarantee that that child will be healthy and live a full life. I think expecting a breeder to provide a guarantee is unrealistic. We dont even get lifetime guarantees on cars or electronic equipment.
What I expect from a breeder (what I try to do as a breeder) is that as much care as possible has been taken to
minimise the chance of genetic issues or problems in puppies. Most caring breeders dont want to bring an unhealthy puppy into the world and cause pain. Some people dont care, some people are ignorant. Puppy millers and such simply dont care. Testing and screening interferes with profits. Pet shops dont care. BYBs and 'Bob down the road' may simply be ignorant. To them Muffy is healthy and fit and so is Fred's dog down the road, and since they're such nice dogs, why not breed them together and sell or give away the pups. They dont even think of health issues that may arise.
In purebred dogs generally, there is information on inherited diseases which can be tested more or less effectively. Where testing is available for something then, if a breeder cares, they should test. Most breeders do. Most BYBs dont as they generally dont really know about it, they dont know anything about pedigrees or belong to clubs and discuss dogs. Breeders usually think, breathe and talk dogs all the time. BYBs breed as a way to make money or as an accident usually. That would be the biggest difference.
Now... on the testing... Some tests are 100% effective. They are DNA tests. Unfortunately they are few and far between. Most tests arent that effective. The test for SA for instance is only effective if it tells you the dog has SA in that spot on that day. If the test comes back clear the dog may still have it or develop it later. After its been bred. And the puppies are already in their new homes and growing up with a timebomb.
I did the SA test on Pagan and Montana. I didnt on Meika. It seemed a waste of time. I know the dogs involved - parents and grandparents. Not affected. I figured that was a better indication. Older dogs who've had SA tests and are still clear are a better way to judge. A BYB wont know things like that.
Screening for things like good hips and temperaments etc are important too. Which is where getting to know the pedigrees and putting in years of knowing the lines and dogs comes in handy. I'm only just beginning to know dogs and lines now, after 10 years. A BYB doesnt have that.
There is always a risk though. We are all only human. We are at the mercy of the information we can get. People dont always tell the truth and often things happen or truths come out after the fact, after a mating has taken place and pups are older. Its how people handle this that makes a difference. People who've found out about epilepsy or PRA in a line and have notified owners of puppies and neutered and rehomed dogs they were showing or breeding from to stop passing on the problem.
As someone who's bought dogs from others, if I had a puppy who ended up getting something like that, would I expect the breeder to refund me my money? No. Not unless I knew they had prior knowledge and purposefully bred the litter knowing full well the pups WOULD get sick. Then I'd be angry. But most people do what they can to do right. And they use the tests and information available to them. And as I said, sometimes information comes too late. At that point, is it the breeder's fault? I dont think so. Would I want another puppy from them? Probably not! LOL I'm also human and I'd be too afraid!
I can see why someone would be afraid by the uncertainty of it all, the fear of finding and picking the right puppy from the right breeder. And yet, time after time, I am astounded that people who go on about health and wanting to be sure of what they get, go out and buy the first puppy they find even when I know that their questions about testing wouldnt have been answered the way they would have wanted them to be.
All I can do, as a breeder, is to be as honest as I can with myself and with puppy buyers. I tell them what I know and what I have done to minimise risks. I do what I can. If thats not enough they can go to someone else to buy a puppy. I will not guarantee health for life. I will provide as much testing as I have on my own dogs and studs going back as many generations as I can lay my hands on. I think health guarantees are unrealistic. I can guarantee that a puppy leaving my home is healthy at the time and that I have raised it to the best of my ability and that I have taken as much care as I can, with the knowledge that I have available to me, to ensure their chances of inherited diseases is minimal. I will be there and support puppy buyers in every way I can throughout the life of my pups. I will take them back and help to rehome them if it comes to that. Its all I can do.
If someone is that concerened they can start researching pedigrees and join the poodle health registry and do research. You'll find that there is NO totally safe and totally clear line when it comes to poodles. Its a small gene pool and all poodles go back to the same original lines. What we, as breeders, have to do is to take into consideration all the information we can get and weigh the risks and take a chance. If we didnt do that we'd never breed a litter. Every single litter is a risk to some extent. A calculated risk or whatever you want to call it.
My experience is that only 1% of pet buyers are that interested in all that background information. Thats why a lot of people buy from the paper, BYBs or disreputable breeders.
Here are the links I mentioned.
http://www.phrdatabase.org/pp_login.htm
http://www.poodlepedigree.com/