The borrower needs to be at least 21 years of age in order to avail of a loan as per the law. However, some lenders might prefer to lend to borrowers older than 23 years.
For education loans, applications are accepted for students who are a minimum of 18 years old.
Do note that age is not the only criteria for loan eligibility. Credit score, income and assets count for home loans, for example. For an education plan, one should have obtained admission and often, past grades of the student are also taken into consideration.