When applying for 2018 health insurance, you need to give them your 2018 Estimated Income. If that income qualifies *AND* the Marketplace accepts your Estimated Income, you should be able to receive Advance monthly credits to reduce your monthly cost of insurance.
If the Marketplace does NOT accept your Estimated income, the first step would be to try to make them accept it by explaining the situation. If they still don't accept the income, you would pay the 'full cost' of insurance each month. However, if your ACTUAL income (and other circumstances) qualify, you would received the full amount of credit ("subsidy") when you file your 2018 tax return.
