Hey you,
I told you this would be a better place to ask this question than on dogchat seen as we're all yorkie owners
If you eventually plan to get both then I don't think it really matters which you get first, as you know I have 3 yorkies and plan to get a maltese.
Depending on the breeder and area of the country yorkies are around £400-£600 and Maltese are around £1200-£1900. I pay about £60 for the initial puppy vaccines and around £35 for each annual one. I have had to visit the vets for a few other things over the years such as Indy's cyst removal and when Ben bruised his leg. Not very often though.
Good luck