The contents of a blind box can be of high value, or the value is not equal to the price, so you need to have some luck when you buy it. Pet blind boxes also have no idea what pets are inside and you need to receive them to know what they are.
Whether you want to adopt a pet cat, or a pet dog, you can look at adoption platforms in the same city, which tend to rescue many stray animals. The point of adoption is not to be free, but to give a home to a stray animal. It is best not to take the form of a pet blind box.