I have both a yorkie and a maltese, and I absolutely love both breeds
My yorkie came first, and when he was almost 3 yrs old, we bought our 7 month old maltese. That was in February of this year. They get along great
For a yorkie, I would say you should expect to spend at least $800 probably more depending on your area, and for a maltese, I would say from a reputable breeder, they start at $1000 for a male and more than that ($1500 and up) if you want a female.
I do know of one reputable maltese breeder that sells her pups for under $1000, so it's not impossible
When you first get your pup, you will have to pay for some shots...It's been a long time since we got the puppy shots, so I can't remember how much. Maybe someone else can help you with that.
You should have money set aside for emergencies or at least have a credit card that you can use for emergencies for the dog(s).
At the very least, the dog should get an annual check-up once it has received its puppy shots.