I'm sure that you must have a vet school in your area that would do spay/neutering for a reasonable rate...have you ever inquired about that? Please make whatever financial sacrifices you have to to see that these animals are properly taken care of. The world has more than enough homeless kittens, not to mention the health risk that you are putting these cats at.
If you are wondering if your dog can count, hide three cookies in your hand--and give him two!!