I've learned more than I ever cared to know. My vet says 3 lbs is minimum. They have litters every 65 days. Can stay in heat 3 weeks at a time. Charges average $55.00 for neuter and $85 for spay at Humane Society up to $143.00 at Vet's because they require shots before they will spay or neuter. At one time we had 3 females pregnant which delivered within 3 weeks of each other. Each had 5 kittens. That is 18 cats, and that didn't include the males who thankfully couldn't get pregnant. We are down to Lil Miss, Scotchie, Midas, Ace, Bandit, Tippy And Casper. And thank the Lord they are all finally fixed!