How old is the pup? House breaking is pretty hard before 12 weeks.
Crate training is a great option, especially if you aren't home during the day. Dogs don't like to mess where they sleep, so they housebreak faster when crate trained.
Shitzus are hard to train to do anything, so your friend needs to keep that in mind. He also needs to make sure that he is using a scent remover when he cleans up floors after the pup. If they can smell an area that they messed, they will do it again in the same place.
Best bet is to walk the pup in the morning, half an hour after she was fed and walk her until she finishes her business. Put her in a crate, or at least contain her in a small area with toys (if in a crate, remove her color) and leave her with just water and a small area behind her bedding covered with newspaper. As soon as he gets home, take her for a walk and spend time with her. She'll get the hang of it after awhile.
I also suggest a can with coins in it as a housebreaking tool. When you see the dog relieving herself inside, throw the can in the general direction (not at the pup) then grab the pup and take them outside and praise them once outside.