even people without enough work credits are eligible for medicare. they just have to pay for part a whereas those with about 10 years of work history don't because they've already paid into the system via taxes. there are medicare savings programs that help people with low incomes cover the cost of medicare. check this page on medicare. gov for more information.
i have a sister who is not 69 years old and not eligible for medicare because she doesn't have the work credits. her income is approximately $17 000 a year. what type of low-cost medical insurance will she be eligible for?