What utilities does a residence legally have to have to be considered habitable?

I have searched everywhere for this answer with zero luck......I live in Indiana and would like to know what utilities a residence legally has to have to be considered habitable. Clean running water? Electricity? Heat? I know a family that has had their gas shut off for months now due to nonpayment, they heat water on an electric griddle for baths for their children and say that they will just use multiple space heaters to heat the entire house during the bitterly cold winter months instead of reconnecting the gas. I fear that their water and electricity both may get shut off soon due to nonpayment as well. I am worried about the 3 children that live there permanently and the other 5 children that visit their parents there every other weekend. Can anyone offer any info? Maybe a good person to ask even? Thank you!