Too many people don't consider the cost of vet care when they purchase their puppy. Toy breed dogs especially seem to have more emergencies, i.e. pancreatitis, dehydration, injuries from jumping on and off furniture.
When your Yorkie is sick or injured it is not the time to be worrying about how you will pay for it. Most emergency vets require that you pay upfront. If you can't, they will turn you away.
I'm not a big fan of pet insurance because there is so much it doesn't cover. The best thing to do is to set up a separate account for vet bills and add to it monthly. Have a fixed sum automatically deposited from your paycheck if possible.
Remember, someday your Yorkie's life may depend on you being financially prepared for an emergency.