I've had dogs all my nearly 62 years. All kinds of dogs. I loved each and every one of them, from mutt to purebred. While I had them, I always thought their breed was sooooo good. But I've never had a second of the same breed ... I always got a different breed.
Until I got my first Yorkie.
Now I have two (they're kinda like potato chips: bet'cha can't have just one!). And I love them dearly. They're everything I could hope for in a pet: small, compact, friendly, protective, cuddly, don't eat much (with good food) and don't poop much, either! Mine are healthy, so I expect them to be around for a while, which can be 15-17 years. My greatest hope is that I will never have to go through the pain of losing another beloved pet, and that my daughter (who lives with me and loves them as much as I do) will be caring for them after I'm gone.
You're going through a bit of anxiety right now. A 7 year old may have some problems, issues. S/He may grieve for it's former owner. But with time and patience, you will be able to overcome all problems. Yorkies are smart little dogs - sometimes TOO smart
- but I don't think you will ever regret your decision.
Good luck - and have a great time.