Anyone who hasn't owned a Yorkie doesn't count as sound advice LOL
What is your boy like? has he been around other dogs? Remember once you bring in another dog they start to act like a pack and can get envious of eachother.
Remember you are the one who lives in your house and knows your pup the best, and yourself. Trust your instincts and know that you have time, it's not like your little guy is going to reach an age and not like other dogs just make sure he is socialized. Take him to dog parks, puppy class etc...
Have fun! this is your life, your money, your home and time.... not your families!
