Pros and cons of a cat

My husbands 2nd job is working at a pet store. Well they have an adoption center in there. One of his many jobs there is to take care of all the animals including the adoption ones. So there is this older cat named jonsie. He has falling in love with her. Well she meet our son (6yr old) and our daughter (2months) today. Our son wants her so bad. Husband says jonsie has been there for months all the other cats come and go but not her. She is the only one that doesnt swat at you through the cage or bites. Or poops on their bed instead of the litter box. We are really considering getting her. What are pros and cons of havimg an older cat with a small baby?