Is it legal not to pay rent in SF?

By law, a landlord must provide a working heater, water, electricity (used to be they had to provide a live telephone line but not sure that still holds with cell phones now) and a certain degree of safety. The landlord is not responsible for paying for the utility bill or heating bill or water bill but the landlord must state that explicitly in the lease/rental agreement. It doesn't matter if the ambient temperature stays at 65F, the landlord still must have some working means for the tenant to turn on and have heat in the area he/she rents. If they must use space heaters to keep the place warm enough and the building is not equipped to handle the amount of power that the heaters draw (or more likely, the apartment isn't set up with enough electrical lines to handle that kind of power draw), the landlord must either provide some other legal and safe means of heating the place, pay fro the tenants to live comfortably somewhere else while the landlord installs a working heater, or redo the whole electrical system so outlets won't overload. The chinese couple needs to research what it entails to rent space in their building.

It is not legal to withhold rent for repairs. They must give 30 days notice to the landlord for repairs, and then if nothing is done make the repairs themselves and deduct it from the rent.

If it's a case of no heat source at all, the landlord legally MUST provide heat. It's quite possible those are illegal units.

It is NOT legal to stop paying rent. You will be evicted. You complained to city already. If landlord does not provide heating, you complain again. If they are foreign Chinese they dont know the laws.

The owner of the property could be in trouble. The renters have a legitimate complaint. City can fine the owners over this and deny them permission to have any renters.

Chinese Tong members make problems go away. Don't ask if this is legal.