Considering adding a puppy

Hi, I have a 15 years old Aussie who is calm, relaxed and sleeps the majority of the time. Frankie came to me at 2 years old, as did my dog previous to her.

We recently moved to a house from an apartment and there is a more space inside but we also have a large yard now.

Because of her age and because the breeder we know has two 4 month old mini Aussie’s available, I have been wondering if it’s the time to add a pup. Or if I’m just crazy to consider it.

I would love to know what I can expect from a 4 month to 1 year old pup that is currently 100% crate trained and 80% trained to pee outside. Pros and cons please .

I would also like to know at what stage do they start behaving less like a puppy?

I would also like to know if I can continue to work part time from home (I only work part time from home) and how folks manage that who may also have a chronic illness?

I also probably should have mentioned closer to the beginning that I also have a chronic illness that comes with pain and insomnia, so would like to get an idea of what I will face with a dog that age, so I don’t get in over my head.
My sleep schedule is kind of messed up and usually there are approx 2 days a a week I feel incredibly tired.

I would have a dog walker to help me since I can’t do long walks.

Thanks.