Wow. That... There are ways to get animals for donations. There are blood banks out there that have animals who are specifically for that program. Blood donors need to be screened for illnesses and need to have the right universal donor antigens. Just... ugh. You get a few freebies for dogs who have never had transfusions or puppies before but that is pushing it. The fact that they paid for services not rendered could potentially be a legal thing there. Keeping pets that were not signed over to you if they are in a state where animals are considered property could potentially help. As property that is legally yours you could make a case out of.
Ugh. Just... so not cool. We have in house donors where I work and there's a vet in town who runs a blood bank with community animals who live with their owners, and only donate for two years, getting a credit for services out of it. My golden and my male kitty both are blood donors where I work and if it caused either of them stress I would not continue doing it, but they are both happy and healthy. :/