You can expect the equilibrium & jealousy. I have a 10 year old female dog and a cat. When my husband gave me my two yorkies it was hate at first sight by my older dog and cat! My older dog is very gentle and sweet. But having two puppy's jumping all over her wanting to play got on her last nerve fast. I ended up giving Rickey (one of my yorkies 6 months old) to my son and his family.
My older dog (FiFi) and Noah get along great now. BUT the cat still hates Noah and chases him every chance she gets. She even pounced on him and bit him!
He loves it....go figure. Noah weighs 5.2lbs and the cat weighs 15!
If you are sure you can give all the animals the time each of them need, then I see nothing wrong with adding to your family if that is really what you want to do. Good luck.
