As soon as 2017, Vermont could become the first state to provide and pay for insurance for most of its residents under a plan passed by the Legislature Thursday. But it must first clear several significant hurdles, including persuading the federal government to allow the state to assume responsibility for Medicare and Medicaid enrollees and finding a way to pay for the program. The bill outlines a planning process for implementing what is often referred to as a "single-payer" system. Called Green Mountain Care, the program would operate in its first few years much like other state health care exchanges established under the federal Affordable Care Act and must begin enrolling individuals and small business in 2014. That's the year the mandate for most Americans to have health insurance takes effect.