I live in NYC and a yorkie is a perfect apartment dog. They do need to be walked because they are terriers but they can be quite happy in a smaller space as long as they get exercise and love
Keoki is wee wee pad trained and outdoor trained. I would recommend, if it is convenient, for you to just outdoor train your baby - because I lived on a 5 floor walk-up and the harsh winters in NYC I trained him for both. Yorkies are the best dogs ever and great for apartments!!!!