Where I live, dogs happen. Four of our current seven were homeless at one point in their lives.
Suzy wandered into our lives when she was about six months old. She cowered outside of the fence, wanting to be with our dogs. She was wearing a belt around her neck. She was terrified of people, but she is completely dog-friendly. She has been spayed and has her shots. She still won't let you touch her, but she will come close enough to take a cookie out of our hand.
Wiley found his forever home through the county Animal Control officer, who found him running wild. He was unadoptable. (He is a jerk.)
A foster took him, and I got him through the foster. He is not the least bit grateful.
Nigel was simply looking for a home where he could demonstrate his Very. Good. Dog. personality. We call him our Boy Scout. He is getting old and going white around the face, and he has had a good run.