There are a variety of types of extended repayment plans, and they depend on the amount, purpose and term of the loan, as well as the creditworthiness of the borrower. Interest only, fixed monthly, and income based payment plans are all available, but not every lender offers them. You should choose the payment plan that will allow you to most quickly pay off the loan, even if it results in slightly higher payments.
Extended payment plans on student loans vary widely. In many instances, payments don't begin until after graduation, but all the while, the loan accrues interest. When the loan's term is up, the student decides whether they want a fixed monthly payment, or a graduated plan. Some of these allow the borrower to make low, interest only payments for up to five years after they graduate; after then, the monthly payment increases.
You should learn about your loan's payment plan ahead of time. Making interest payments can keep that amount from being added to the principal, and will decrease the amount you pay over time. Some lenders offer an income-based option. Most are fairly straightforward and include a monthly payment made up of both interest and principal.
Mortgage repayment plans can also differ from one lender to the next. In a conventional mortgage with a fixed rate, the payment remains the same for the duration of the loan. However, over time, the amount paid in interest declines while more is put toward the principal. Some lenders offer interest-only mortgages, which allow borrowers to make payments toward the interest only for the first few years of the loan term. This usually results in a "balloon payment" at the end, which can be very high and take you by surprise if you aren't prepared. Another viable option is to make more frequent payments on your mortgage; paying more often can take the interest down more quickly and reduce the overall amount you pay.