The lack of income and/or assess which prevents one from obtaining a subsistence level of functioning?

The situation you described is known as poverty, which is the lack of financial resources and essential goods or services needed to maintain a subsistence level of functioning and basic standards of living, such as food, shelter, and healthcare. This state can be further categorized into absolute poverty, where basic needs cannot be met at all, and relative poverty, where one's standard of living falls significantly below the average in their society.