Maltese have very soft coat that needs a lot of maintenance...I have known a couple that were very sweet but they need a lot of daily brushing to not mat. And a Maltese is a toy breed, so all are small. If someone is selling teacup or extra small Maltese I would look elsewhere. IMO, theres no need to breed a very small dog to be extra small and that can lead to issues.
Pet stores that sell puppies often get them from sources where the breeding dogs are not well treated. I would look for a Rescue or a reputable breeder.