i wouldnt reccomend a collie they are 24-7 jobs need stimulation all the time and they like to be boss

I wouldn't have said a collie either never owned one but just seeing them out and about makes me realise they are pure "need to do" dogs.

Not sure about Shelties though - maybe a thought the one I knew was very gentle.

I have 2 Red Setters and a Pug (those are the ones that go on walks, Sausage the Griffon is too old and just pootles around the garden).
Buggles, the Pug (did you guess that? ) goes on the same walks as the Reds(1 1/2 to 2 hrs a day) and copes fine. He just stays by my feet and does not do all the running around and hunting that the Reds do!

Why not get a rescue dog? then you could see how they get on before commiting. You could always get a slightly older dog that would not be so stressful on the yorkie, loads of old/er dogs need homes and they would prob make a calm companion for the little fellow.