I'm thinking of getting a doggie and a cat

[Morbius]

39. We adopted a dog four years ago.

He was originally brought to the shelter by a woman who told them the dog was fine, but the cat wouldn't leave him alone.

The woman who adopted him next kept him in a crate while she was at work, and she worked full time. When he wouldn't go back in the crate she took him to the shelter.

The next family who adopted him brought him back almost immediately, because he bit someone.

We first met Dozer (that's his name) and fell for him right away. Then they brought us his history, but it was too late. We were in love and determined to make it work. But it was a struggle. Dozer had PTSD, for want of a better word. Startle him when he's sleeping and he's quick to try and defend himself. We sought out an expert trainer to train us to train him, and he's better now, but still we must be careful.

The bottom line: some cats are fine with puppies. Some are definitely not. Just as different dog breeds manifest different behaviors, so also different cat breeds act in their own way. Never adopt an animal without learning their history, and educating yourself about the breed. Particularly the behaviors and health issues associated with it. The idea posted about adopting an older dog who has already lived with a cat sounds smart to me.