Also remembering that certain animal companions are not just pets - they do a lot more than keep their human companions company. In some cases it is the animal that is doing the 'caring' 

Examples:-

Hearing dogs www.hearingdogs.org.uk/
Guide dogs www.pathfinderdogs.org/  & www.guidedogs.org.uk/
Dogs for the disabled www.dogsforthedisabled.org/  &
Monkey helpers for the disabled www.monkeyhelpers.org/

yes, if you get it right, it's a two way thing to the benefit of both parties.  'Ownership' is then a two way street.  One side pays cash, both sides are rewarded.