Allowing non-housebroken dog to move in

DownTheAvenue wrote:
Any dog at any age can learn a new behavior. However, some dogs are more likely to respond to learning than others. In this case, I suspect you will have quite a challenge, as you have three issues working against you. One is the breed- Chihuahuas can be stubborn and not very bright. Two is the accepted behavior that is now unacceptable has been ingrained into the dog its whole life, and you are asking for a change not just to learn something new. And thirdly, you need absolute consistency- everyone must be on board into managing the dog to go outside, and I doubt your mother will cooperate.

Confining the dog to a very small area or crate and taking it out hourly, after eating, after waking from a nap, and any activity helps. Restricting water intake later in the evening helps over the night.

1) Who told you they aren't very bright? I suspect, you are confusing owners treating small dogs different from large dogs and then wondering why they don't act the same as large dogs. Ours certainly didn't qualify as "not very bright".
2) Ours was from the pound and took almost no time to train but we had the advantage of having him with us all day, so we could stay on it. Also, since we were living on the boat at the time when we went through a stretch at anchor, we picked up a litter box (actually a 6" high storage box for under the bed) put a green rug in it and within a week had him using that reliably.
3) I will agree if mom or the kids don't follow thru, it will be a challenge as that's giving conflicting messages to the dog.