adopting shelter animals instead of buying pets

I’m wanting to get an idea on how to begin my definition essay . I want to cover the importance of adopting a pet from recuse shelters rather than buying . The points I thought to make about was that buying lets say a purebred puppy could be supporting a puppy mill. Also how a pet that came from the street can make the best companion and even if they are older you are providing that animal the best last moments they may have