How will custody of a 4 year old work if father is unemployed and mother works 5-6 days a week?

Husband and wife split. They have a 4 year old. The husband does not work. He gets a government check as long as he attends classes because he was in the navy. Mother works full time. Takes care of child's needs such as school, clothing, medical benefits etc. There are also some outstanding medical bills for the child from when they were together. There is also a small mortgage loan which the mother put under her name but was forced to leave because of difference with her husband at the time. The husnand remained a tenant but the wife left.She's been thrown into collection agencies agencies because he failed to pay the rent. How do all these outstanding bills get split. They have been separated for a year and the father of the child does not provide any type of support for the childs expenses. Please advise.