I have two Yorkies, they are 3 years old bother and sister....I also live in an apartment and was forced to pee pad train them, it can be expensive as they pee a lot. However I buy their pad at discount stores so they are a little cheaper. I read is hard to keep Yorkies fully trained to pee on the pads, and it is true. my Yorkies if I don't constantly praise them they will poop and pee off the pad, so I had vinyl planks installed in my whole apartment and that helps with the clean up. Yorkies can't be left alone for long periods of time, they get anxious and will poop and pee off the pad. Don't punish them but praise them when they do their business where they supposed too.
Yorkies love praise and treats and they like to make their owners happy
Good luck with your move, maybe you can find someone to check on him at least once when you are at work.