Mmmm....I am very hesitate to tell anyone to do something they shouldn't....and I hope the OP strongly considers what some on here have suggested she do....like just not put down her step dad's info.
According the the FAFSA website, the OP must note her step dad's income on the FAFSA. Doesn't matter if he is going to help her pay for school or not. He has supported her so his income counts - remember, mom doesn't work & dad is MIA, so her step dad's income is relevant.
Plus, her mom isn't working which means that she would have to say there was NO income coming into the household???? All income (child support, alimony, welfare benefits, etc.) must be noted as income on the FAFSA. Since mom isn't getting alimony, child support or welfare, how is she supporting her family????? Talk about setting off red flags.
While it may seem easy to just say, uh, my step dad isn't contributing so I don't have to put his income down, let's not forget the FAFSA is a legal governmental document. OP has to sign it saying the info she put on there is true. So, if she gets caught lying, she will likely lose all future hopes of receiving financial aid.....and goodness knows what the penalties are for putting down falsified information on the government doc.
Also, even though the step dad isn't helping her pay for college, if she stays home while attending school, he is contributing minimally to the roof over her head, food, utilities, etc.
I would suggest that the OP call FAFSA directly -- 1-800-4-FED-AID (1-800-433-3243) to clarify what is on their website and their instructions (which does indicate she must list the step dad's income). Of course, emancipation is another option.
Someone noted above that they thought the parents had to sign for the loans. Well, that depends....Federal Stafford Loans are signed by the student because the loan is their responsibility to repay. There are two types -- subsidized - government pays the accruing interest while the student is in school and unsubsidized - interest accumulates. There are annual and aggregate limits on both depending on the grade/credit level (freshman, sophomore, etc) If the parents choose to take out student loans to help their child pay for college, they take out & sign Parent Plus loans. More info is available thru Sallie Mae. Just do a search for them.
To the OP, good luck! Try not to worry too much. Take it step by step. Start early so you have plenty of time to handle the unexpected. Who knows, you may not have anything to worry about, but you won't know until you complete the FAFSA.