If you are really poor, you get government run healthcare call Medicaid for free. Medicaid has been around since 1965. Medicaid is one of the most efficient forms of health care out there (results/$ spent). Some doctors do not like it for Medicaid pays less than what private insurance would have paid for a similar procedure, other doctors are fine with Medicaid since they are still getting paid and if the really poor did not have Medicaid then they would not pay at all, and if it was an emergency situation the doctor would still have to treat them at a loss (note this last sentence is really really simplified and it is far more complicated than that).
Medicaid is run by the states and is funded by both the US federal government as well as the states. Prior to Obamacare, Medicaid eligibility since it was run by the states was very much social engineering, some states would not allow you to be eligible for Medicaid unless you were a parent or caretaker no matter what your income was, while other states prior to Obamacare would have generous Medicaid eligibility.
Medicaid under Obamacare change that. If a state choose to expand Medicaid under the new rules of Obamacare (more on that later) and cover people up to 133% of the poverty line (about $15,520 for individuals and $31,720 for a family of four) the federal government would pay for 100% of the expansion for the first 3 years, and 90% of the expansion for years 4+. So in effect the US government would be taking the entire tab for the Medicaid expansion.
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If you are poor but not really poor ("in poverty") Obamacare would have a subsidy for you.
You would be required to get health insurance or pay a penalty. If you bought health insurance through something called the marketplace exchange you would get a subsidy. These marketplaces exchanges would either be set up by your state or by the federal government if the state declines to do so, and would allow you to buy private insurance plans offered in your state that meet minimum requirements of coverage. Thus we are talking about private insurance here, but the government pays part of the bill and the patients pay part of the bill.
You would get a subsidy if your income was between 100% to 400% of the poverty level on a sliding scale. Thus for example if you had a family of four on $40,000 income, a silver policy plan may cost you $8,000 dollars a year without a subsidy but with the subsidy the insurance plan would cost you $2,000 a year while $6,000 would be paid by the federal government (where the government gets the subsidy money is something for a different time, pretty much I am tired of explaining but Obamacare is revenue neutral according to the cbo), thus this parent can get health insurance that costs him about 5% of his income and the family has health insurance, if they pay the penalty instead of getting insurance in 2016 they would pay a penalty of 2.5%.
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Now in theory the Medicaid expansion was supposed to cover the people under 133% of the poverty level, and people 100% to 400% of the poverty level would be covered by the exchanges. The supreme court last year allowed the states to keep their old rules for Medicaid if they wanted (but not get the extra funding), or they can go with the new rules of Obamacare (and get the extra funding.)
About half the states in the US (mostly red states) have not expanded Medicaid eligibility. Thus for example if you were a single individual in Texas that made less than $11,670 you would not get a subsidy to buy health insurance, and you would have to pay the health care penalty unless you get a waiver from the US government. That means you lose $95 dollars in 2014, and this would increase to $695 dollars in 2016. This is because you live in a (red) state that sees Medicaid as social engineering.