Saints do NOT fall into this category. Breed choice will also determine, to a large degree, the amount you'll spend on vetting your dog. Both of these require planning, and the second requires alot of work. Every time you see a dog chained in a yard, or pooping on the sidewalk without his owner waiting to clean up after him, or running loose down the street, be prepared to take action. If you see a dog running at large, either call the animal control officer, slip a note under his collar explaining responsible ownership, or put a leash on him, and take him home yourself.
Education is the key.