Check this out!
Some don't start until you apply so it's helpful to plan ahead of time.
Also, if you're not making much in school you can request to have an in-school deferment waiver. This means you can start making "payments," often $0 on an Income-driven repayment plan. These payments would start your forgiveness early. When you get out of school you'll already have years of payments counted towards your forgiveness requirements!