It's usually years before genetic time bombs start going off in poorly bred dogs. My Lady was perfectly healthy for the first four years of her life. It now costs
$5,000 a year for all her medications and diabetic supplies and another $1,000-1,500 on top of that for vet bills.
The key is to buy a puppy from a reputable breeder, not rely on a health guarantee. Does this breeder have all her dogs tested before breeding? By health tested, I don't mean a routine physical done by her vet. I mean bile acids tests, CERF for eyes, knees and hips screened for luxating patellas and Legg-Perthes, thyroid panels, etc.
Did you know that Yorkies are 36 times more likely to be born with a liver shunt shunt
than all other breeds combined? Ask this breeder if all her Yorkies have had bile acids tests and ask to see the results. If they haven't, I would not consider buying a puppy from her.
Just look in the Health and Sick sections here on YT to see all the members who are dealing with genetic conditions like liver shunts and luxating patellas. Both cost thousands of dollars to diagnose and surgically repair.
Getting your puppy from a reputable breeder will save you lots of money and heartache in the future.