My first was supposed to reach 7lbs in weight as I didn't think I wanted a tiny one....that is her left, TARA, and she only grew to 4lbs !
She has a collapsed trachea, and was only supposed to live to 4yrs at most so the vet said. What tripe that was....she is sooo full of beans ! I keep her settled, but she still goes demented round our livingroom, and runs accross half the huge beach to say hello to some stranger that she thinks looks nice and who should be speaking to her, "the queen" !!!, and runs back full pelt to our heels - quite chuffed with herself !
She does have coughing fits, but not often, and I just massage her throat, and it comes ok. It doesn't phase her at all. I think she will live just as long as others. She is spayed.
My other two, CASPER and TAMMY are 4lbs too.....and have no health problems at all.
I love their size now.
I think small is fine, you just have to be carefull with them....the thing is they think they are
huge, and will shock you at their behaviour of not being any different to any other dog !
So don't be too concerned about size....it depends on the dog. Any dog can have health problems. Just look very carefully at the parents of puppies, and conditions, talk to their breeder, and for goodness sake, don't do as many of us do and fall for the first pup you see....
says she who has done this herself, lol - easier said than done !
......Look at a few puppies from different breeders.
Also, you could choose to see yourself as the good samaraton and give the not so perfect one a good home....invest in good pet insurance and just take each day as it comes....enjoy every day you have with it, and if it isn't a long living dog, know you gave it a happy life for however long it had.
GOOD LUCK !

DEBRA x x x