At the present time, the ACT is offered in 19 States, for free. 20 States offer the SAT for no cost.
However, be aware, these tests are scheduled by the Department of Education, in each State. For instance, Colorado (where I live) has a State-wide SAT test on April 13th. The College Board is administering the Spring SAT March 9th, and then, again, May 4th. The May 4th test date is, also, the test date for the Subject exam. So, as always, planning is key.
Since these exams (both the ACT and SAT) are administered through the Dept of Ed in each State, they are given on school days.
This has big advantages.
1) It's a free test! College is expensive, so any savings will help toward future tuition.
2) If you're, already, scheduled for one of the National test dates, this will give you a practice test.
3) You won't have to give up a Saturday to sit for the exam.
If you happen to live in a State that doesn't offer a free exam, and money is tight, there is another option. Both the College Board (for the SAT) and the ACT offer a fee wavier.
You do need to meet certain criteria.
-You're enrolled in or eligible for the federal Free and Reduced Price Lunch program
-You're enrolled in a federal, state, or local program that aids students from low-income families (like Upward Bound)
-Your family receives public assistance
-You live in public housing, a foster home, or are homeless.
-Your household income level falls below USDA levels for Reduced Price lunches
Your school counselor will help you get the fee waiver. You cannot apply directly through the College Board or ACT, Inc. Of course this all takes time, so plan ahead. Figure out when you'll be taking the exam and get in contact with your school counselor. They will help you with the process.
One of the biggest challenges, most students face, when contemplating college, are costs. If you take a little time, you can help reduce them, starting with the exam that going to help you get into your dream college.