When doing my FAFSA, my EFC turned out to be 1/2 what I thought it would be. When I went back to check it over I realized that what caused it to go down so dramatically is the fact that my spouse will also be attending school. He'll be working full-time as well, but since he'll be taking enough hours to be considered enrolled half-time, the FAFSA figures it as two students being supported. Just throwing this out so that if anyone's spouse is considering going back to school to finish up their degrees or get new ones, it could be very helpful to your EFC.
PS - The school that my husband will be attending (online) only costs $2,500 per semester for part-time and his company will re-imburse him, but the FAFSA doesn't ask for that info. The Need Access app does ask for all the details, though.