If you don't make much money, there are prescription advocacy programs like this one that one can take part in. However, if you don't make a ton of money, it seems to me that you're likely to be on Medicaid. Does Medicaid not pay for prescriptions? I'm trying to understand the circumstances in which you'd actually want to take advantage of prescription advocacy programs.
I know that Medicare takes care of prescriptions via Medicare Part D.
From medicaid.gov:
Although pharmacy coverage is an optional benefit under federal Medicaid law, all States currently provide coverage for outpatient prescription drugs to all categorically eligible individuals and most other enrollees within their Medicaid programs.
This is related to the Medicaid Drug Rebate Program, which
offsets the Federal and State costs of most outpatient prescription drugs dispensed to Medicaid patients. Approximately 600 drug manufacturers currently participate in this program. All fifty States and the District of Columbia cover prescription drugs under the Medicaid Drug Rebate Program
I can't give you any specific details about patient assistance programs, but rxaccess.sd.gov links to information about various patient assistance programs and general information about Medicaid's and Medicare's prescription drug offerings. It's conceivable that you may be eligible for a patient assistance program but not Medicaid (for all I know, the reverse may be true) but it's difficult to tell without contacting the specific company. Some patient assistance programs only apply to generic versions of the drug, while some state Medicaid programs will pay for brand names. Obviously this varies from state to state.
