The Messenger of Allah ﷺ forbade taking payment for a dog, except for a trained dog.
حدثنا عباد بن العوام عن الحسن بن أبي جعفر عن أبي الزبير
نهى رسول الله ﷺ عن ثمن الكلب إلا الكلب المعلم
No references are available.
Its chain of transmission is hasan, because of Hasan bin Abu Jafar, they criticized him for his poor memory, even though he was a man of merit and righteousness. The hadith is found in Tirmidhi 1281, in the Book of Sales, chapter 50, and there is criticism there as well, from the route of Abu al-Mahzam. The hadith has been narrated with a chain more sahih than this one. See 10437, 10438.