Given your circumstances, I would probably be even more leary than you. I'm not sure what you mean by "expensive". Most healthy Yorkie puppies will start at $1200 or $1500 and up. If you come across someone who claims to be a breeder selling for less than that, the chances are very high that it's either from a puppy mill, a backyard breeder (people who breed for fun or who breed to make money off you), and without any certainty about the puppies health.
I personally would not buy from this older couple. People can be very nice. Nice people don't necessarily know how to properly breed dogs. Nice people who have bred dogs for many years, don't necessarily breed with good ethics, whether intentionally or unintentionally (they may just not know any better without the help of a proper mentor). Pictures of puppies always look cute. But puppy pictures cannot ever tell you how healthy they are or what they will look like when they're full grown.
If you want a healthy puppy, I'd suggest you contact your local dog show organization (
North Arkansas Kennel Club, Inc.) and ask for contacts - perhaps names of Yorkie breeders who have competed in the past (apparently the last show in your city was in February).
Otherwise, if cost is an issue, I'd highly suggest that you keep your options open in terms of the breed and look into adopting at your local shelter or rescue organization. Most shelters have had their dogs checked by a vet and any known conditions (if any) would be revealed.
But most importantly, please take your time and don't rush into buying a puppy. You'll appreciate waiting for as long as possible to find the perfect healthy puppy that will be with you for the next 12-18 years (versus rushing into getting the very cute puppy you saw in a picture that may be sick/unhealthy and end up costing you thousands in vet bills and possibly not living a very long life).