Quick note: many pet suppy stores deal exclusively in cats from the Humane Society. Check out where the cats/kittens are from. Often the cats featured at these stores are having a "last chance" to be seen. Our PetSmart and our Global Pet stores feature cats only from the Humane Society, as does one independent Pet Supply store downtown.
http://pets.petsmart.com/adoptions/
At Global and downtown, the cats are residents until they are adopted.
As for kittens -- you'll have to kitten-proof a house, and if no one is home during the day, perhaps a room can be kitten-proofed until he/she is old enough to roam free during the day.
Everyone adopts the kittens. Few adopt the cats. The hardest cases are older cats. Many of them belonged to seniors who have passed away and they have been put in a Shelter in the hopes of adoption. This after years of a stable home. Please look into the older cats -- they have nothing but love to give.