Elmore, I think it would be best if you don't add a dog to your household. Three cats are plenty in a place your size. I also think it would be difficult for you to take a dog for walks several times per day. Also, dogs are quite expensive; their vet bills seem to be way higher than for cats. I think you have done a wonderful thing rescuing Annabelle, Thatch, and Stella. To add a dog would upset them.