Don't worry, first time college students all worry about this since you don't hear about all this. It's fairly simple, actually. You have to pay by the semester, but you do get offered financial aid from the school, which is determined by what you submitted in your FAFSA. Basically the FAFSA looks at you and your parents' tax records and determines what amount of financial aid you can be offered by your income. I'll warn you that the loans will have to be paid post-graduation, but grants and scholarships are basically free money that pays your tuition. My recommendation is to apply for as many scholarships as you can to avoid any college debts.
You don't actually have to take the ACT if you've taken the SAT. The only reason to do it is if you're going into a specific program at your college that requires scores of both kinds. These are usually your medical related programs like pharmacy.
Pretty much you do have to pay before attending classes. This doesn't account for your books, which you have to buy separately. Fortunately, since you register for classes ahead of time, you can order your books online (like half.com) and get the before school starts. Of course, most professors give you a deadline after classes start to account for online book orders. (Some will be cool enough to let you borrow books from them or the library if need be.) Some schools also have a rental option for textbooks, but you have to absolutely be sure to take good care of the books or they'll charge you for damages... just like the library.
Let's assume you still don't have enough saved to go to college. You can set up a payment plan with some schools if you have financial troubles. You'll have to contact the financial aid office at your school for details. (Don't know it? You can always look up the school's website and it should be there.)
My opinion is your best option is to work for a year to save up money and for you to really make sure you know what you want to go to school for (biggest mistake students make is to not know until AFTER they graduate college). You can apply for a job after you get admitted to your college as well to help pay for anything you need. You can also go part time, but you won't get as much financial aid... though you're not attending as many courses either.
PS, there's a lot of paperwork you go through when it comes to loans. It's intimidating, but don't worry about it too much. I wish you the best. :)
