No, you should be able to determine if you're eligible for a subsidy before you shop for a plan and then have that subsidy applied to any qualified policy you apply for.
Any person who is a U.S. resident and is a U.S. citizen or a U.S. national and is not in jail can apply for a government subsidy and they may qualify as long as they meet, among other requirements, the household income requirements. Under the new law, a person whose household income is between 100% and 400% of the Federal Poverty Level will be eligible for a premium tax credit to reduce the cost of coverage. A person with household income up to 250% of the Federal Poverty Level will be eligible for cost-sharing assistance, as long as they are enrolled in a silver plan.