My 2nd yorkie, Daisy, will be around 4lbs fully grown (or so I am guessing). Sophie is 7 mos old and is 5.5 lbs. Daisy plays really rough with Sophie and hasn't been harmed by it at all. She will also crash when she's tired. Really, really tired
SHe is sleeping thru the night, even though her bladder is much smaller than Sophie's. It took almost 5 weeks and we got her at 9.5 weeks.
I keep her in an x-pen when I'm gone. It's 10 panels and is about 50 sq ft. She has her bed, toys food/water and pee pads there. Sophie stays there as well. At this point, Daisy is as trained as Sophie is! LOL I am slowly giving them more room to roam when I'mhome, *after* they've pooped &pottied!