A Chihuahua is a dog. Dogs can be trained to not potty inside the home.
Schedule meals and potty times and stick to the schedule. A Chihuahua needs three to four meals per day depending on age (talk to your breeder). He will need to go out to potty at every mealtime, first thing in the morning, last thing at night before bed, and every few hours in between. Figure on one hour per month of age, up to six hours – or eight hours overnight.
Confine him in a crate, exercise pen, or gated small, puppy-proofed room whenever you cannot keep your eyes on him.
Supervise him anytime he is loose in the home. That means you must have him in sight at all times and be paying attention to him. If he starts sniffing around and squatting, scoop him up and rush out to his potty spot. Encourage him to finish going there and then praise him when he does, which means you should stay there while he is going. When you take him back inside, confine him until you have cleaned the accident and then sprayed it with an enzyme cleaner or white vinegar to remove all odor (remember that a dog’s sense of smell is much greater than ours). If it smells – to him – like a potty spot, he will go there again.