I think folks are being a bit tough on the OP (though I definitely understand where y’all are coming from).
The size of the dog is an important issue, so I can understand why a purebred would be a “known quantity” in that area. But at least via rescue groups (maybe less so at a shelter?). there seem to be many mixed-breed puppies that are mixes of two (or more) small breeds, and are virtually guaranteed to grow up into small dogs.
Raising a puppy is hard work, and I can understand why a first-time dog owner would want to reduce uncertainties as much as possible. But I think a small mixed-breed or purebred from a foster environment might be an excellent bet. Rescue groups really make an effort to get a good sense of their animals’ temperaments and to make sure that the animal and its forever home will be a good match.