I have two little ones and I also live in an apartment on the 4th floor! We use wee wee pads. We keep one in our second bathroom (tile floors). We also keep one in the living room (wood floors) but this is only temporary till our puppy gets better at peeing. I buy them in large packs online from amazon or walmart, it's cheapest that way. Plus you'll need them! You should def. let your puppy sleep in your room in his bed. Dogs like to sleep near their pack
Hope that helps. Good luck and congrats on your new baby.