Our family used AMS for undergrad tuition payments. It is a great way to avoid loans. No need to pay the full tuition price at the beginning of the semester.
The monthly payment is the yearly tuition cost divided by number of months you choose to pay (usually 8/9/or 10). I am not sure how they make money other than the sign-up fee (?$75) and if your monthly payment is not in their office by due date they charge an extra $25 for that month. I think you can have payments automatically taken out of your checking account to avoid any of those fees.
AMS has a list of colleges that "belong" to their program.
There are other programs/companies that run this type of tuition payment. Another one has the initials TMS. (sorry i cannot remember what that stands for).
I have used these services before and the fees are their income. They do not front any money for your tuition, they merely guarantee the school that they will receive your tuition in installments... the school must agree to accept the payments over time. I am not sure what happens if you default on the payment schedule... I presume that you will owe the money to AMS since the school has already been paid.
Save yourself $50/yr.. borrow 1 semesters tuition from a relative and set up your fund; repay the fund with 5 monthly installments and it will be ready for your next semester. At the end of your education, pay the loan back!