You can find a lot of puppy collars at thrift shops for pretty cheap - would never pay full price for one. I'm getting mine at 14 weeks and was told that 8-12 inches was what was being used - then at 4- 6 months graduate to 10-14 inch collar.
I had nose surgery a few months ago and when I got home I was worried the dogs would be so excited and jump all on me, but it was crazy how mild mannered and dare I say tame/domesticated they were. I swear they knew I was hurt and gave me a day or so of good behavior. They are truly great dogs to own!
Isis is darling! By all means do a 'well baby' visit with your vet, and order the DNA swab for fanconi, huge peace of mind. I had a wonderful Isis many years ago, I love the name!
If you find that you have excessive collars/leashes, you may want to call your local shelter and see if they would like to have them. So many shelters run on such a shoestring budget, it might be something they'd be able to use but not afford….
Just a thought