Raindropvampire, thanks for that info. I had looked for no-kill shelters and programs like you mentioned, and I found no no-kill shelters, but I did find a couple of spay-and-release programs (one in my county, one in the next county over), but they didn't offer prices like you're saying. One told me they would give me a deal if it's several cats, but it would still be around $30 per cat. I'll look into your link momentarily. The only problem I have is, at a vet, they have a crash cart, so if anything happens to your pet under anesthesia, they have a chance to revive it. And the cats need to be cared for inside our home after surgery, don't they? I'm not against that, but just trying to see if it's feasible with upwards of 15 cats. One is very pregnant, if I didn't mention, and I'd like to bring her inside (if she'd come) and help with the birth, make sure everything goes okay.

Yoda, we don't use litter boxes for the cats; they use our yard, too. We don't have an actual porch, just steps. Thanks for the suggestion, though.