My husband and I have lived on the combined income of one schoolteacher for our whole married lives so we can do the worthwhile work we love. There are medical procedures that I have put off for over 20 years for myself because I can't afford them (we have expensive health insurance, but it eats up available funds and won't pay for anything until I've topped $7000 out-of-pocket per year).
So, we have had pets over our 30 years together: several feral cats that I've tamed, a couple of goats, parakeets and tropical fish. With each animal, I consider at the start the simple reality that vet care will be only what I can afford: vaccinations, stitching up wounds or very minor surgery. I ask myself whether I can give this animal a good and happy life within those constraints, and recognize that when the animal begins accumulating "old-age" problems I will probably not be able to accomodate them and will more than likely have to have them euthanized.
The creatures we've adopted enjoy their lives with us, experience what would be a long life-span compared to life in the wild, and die a relatively peaceful death. I love my pets dearly and am grateful for the ways they enrich my life, and I believe I enrich theirs, as well.
And I recognize that they are not particularly troubled by thoughts of death the way people are. They live, they enjoy life, they die. And they all live on in my memory.