Welcome to YT
Hair - Yorkies have hair and therefore prepare for grooming, unless you cut them real short. Grooming can be fun for you both if you do it right
Teeth - They have to have their teeth brushed regularly and they don't like it at all (most of them that is). Around 7-8 months you must get the milkyteeth that hasn't fallen out pulled out by the vet.
Cold in winter - you'll have to spend money on a warm jacket. If it's a bitch she will need warmth on her belly - not easy to find a good coat, but here on YT there are several people who sell good coats. (And make them)
Rain - Yorkies don't like rain and you can have a hard time convincing them to go outside for a pee if it rains.
House training - it takes forever and you would go nuts if they weren't so goddarn sweet. Luckily their poop is very small and if you stick to dry food, also quite solid.
Temperament - you have to teach a yorkie who's leader of the pack from the beginning - puppy training is very good. Otherwise you could end up with a house tyran.
Yapping - not all yorkies yap a lot but some do. It can be hard work to teach them not to and some will never learn 100% - it's their way of communicating.
Size - you have to learn not to step on them - slowly you will learn to look down before you move your feet.
But every yorkie is different and you could get a yorkie who loves rain and toothbrushes. So it's hard to say what will drive you nuts. But from what you write about your self, I wouldn't worry about it - you'll be a great yorkiefriend
Good luck
Mette