I went through the exact same, and then decided to get a little Shih tzu. A few weeks later diagnosed with grade 3 aggressive breast cancer, and thought I would have to rehome her.
We coped through months of chemotherapyand radiotherapy, and a year on I'm still having treatment. I've walked her even after chemo, and believe she was my little angel sent for a reason to get me out of bed.
Very hard work with a puppy,and I did try a rescue dog but it went for me twice in 24hrs, but thankfully was on trial.
Mine is very costly as on special diet, and needs clipping every 8 weeks at £30 a time. Add on vaccinations, vet bills, kennels for holidays and pet insurance. Also I'm always watching the time when out, so very restrictive.
On the plus they are company and good excersise.
Would I do it again...not sure I would, but she has been good for me, and lifted my depression.