We got a "free" dog that someone had tied to the tree across the road a few weeks ago. Long story short, it was chipped, guy dumped it and another somewhere else. Animal control said we could have it, kids were begging, wife approved.
A month later, I think we've spent close to $1,000 on this "free" dog. Between initial vet bill for shots, checkup, flea treatments at the house (he had them, feral cats, possums, coons, a fox, etc around, so we already had a few), kennel, harness, collar, leash, treats, dog food….
Free ain't free!! Although with a cat, I'd probably just turn loose outside and the feral cat colony would claim it. Let the crazy cat lady in the box car that drives around at night feed it.