Its good for single mums and the kids to have contact with non single mums and dads too.
Although hostel type accomodation maybe OK for mums with little babies it is in not a good thing to have kids in institutions.

I think house sharing is good as you get the support of others as Dianavan says help with childcare, taking turns with cooking, but it does give the kids a very one sided view of live with no men in it.