I have had yorkshire terriers for years and have never had problems with them. Mine have always been boys and have been castrated. If you do not have them castrated, they will still leave their mark in the house. Obviously if you are going to leave them all day, they may well become dirty. Mine are never left more than a few hours, although occasionally longer. Never had any problems. Also, I would not feed the animal on too richer diet. My used to have chicken with a James Wellbeloved all in one food, often had the runs. Better to get the small dog pouches that are now on the market and use these with the mixer. Hope this helps. Will look again to see if you need any further info.
Sue E