I am in Greece
Rescues are out of the question where I live, let alone breed specific rescues.
Everyone told me to see the dog’s parents, but what exactly should I check on them? I am no dog expert and I could easily overlook something important. Is there something specific I should look for or just the general appearance of the parent?
Are the parents there, to start with. Many unscrupulous breeders will go the “box of puppies in the back of a car, let’s meet up in a shopping center parking lot” route so that buyers can’t see the conditions the puppies are coming from. A responsible breeder will probably strongly suggest, if not insist, that you come see the puppies for yourself and interact with them to see which one is the best fit for you and your family. At least the mother should be present with the puppies; some breeders will have the sire as well, but sometimes the father is owned by a different breeder.
A responsible breeder will also ask you lots of questions when you contact them and ask about getting a puppy. They’ll want to know if you’ve owned dogs before (and what kind of dogs), what your living arrangements are like, are there small children or other pets in the home, what your general daily schedule is like, etc. If a breeder doesn’t seem interested in knowing what kind of home the puppies they breed are going to, they’re probably not a very responsible breeder.
I’m not too familiar with the kennel club circuit or breeders in Greece, but here in Finland, most breed organizations will be up-to-date with breeders who currently have or are planning litters and will be happy to give you contact information.
Ok, looks like I’ve found a reputable breeder. She’s listed on the local kennel club too. Some complain that her puppies are not “real” Maltese because they are a bit smaller than typical (not teacup size though).
Apart from that, her puppies are healthy and she has a 4 month old for sale (she doesn’t sell them younger than 3 months). I will go see it one of these days and probably buy it. 
Four months is a wee bit old for selling a pup (was there a problem with it that preventing it from finding a home sooner?). If not, and if the pup has been properly socialized with humans you should be OK. The real problem is with older pups that have spent the vast majority of their time with other dogs and don’t relate to people well enough.
By the way, having nice-looking and well-behaved parents is no guarantee the pup will turn out the same way (it could take after its crazy Uncle Arthur).
So, got a puppy yet?
I don’t think four months old is too old if the breeder is doing things like socializing the dogs (i.e., getting them out to meet different kinds of people and other dogs, so they learn how to behave).
There are lots of problems with breeding down for smaller dogs. Purse-sized dogs.
If the pup has spent his four months with his dam and littermates, interacting with a human family, getting the proper shots, and being taken out to see things in the world, I don’t see a problem with that age. He should be housetrained by four months, though–or anyway pretty reliable. That is a plus!
A friend got a dachshund puppy, 8 mos. old, from a breed rescue. This poor dog had been returned twice because she “couldn’t be housebroken.” The rescue put her with a foster family who worked with her, and didn’t let her be adopted out until she was. If the breeder hangs onto them until they’re three months old, then four months is not a red flag at all.
The thing about the parents is that the puppy will likely have their temperament, and that way you can see what it’s going to look like when grown, how bit it will be, coat color, things like that. (I always get pound puppies so I have no clue what size they’ll be, and they’ve always been great dogs, so I don’t even know why I’m giving this advice, except it’s supposed to be ideal.)
According to the local law, breeders can’t sell a puppy that is younger than 50 days.
And yes, the puppy is house trained.