If you are a student, you can apply for the . If you have your own income you can apply for any credit card for people with no or limited credit history.
In general, interest is not charged on purchases if the previous balance is paid in full by the due date each month. If you missed at least one due date and failed to pay the balance, the interest charges will start accrue. So if you make a purchase close to due date and fail to pay it off, you will be charged the interest next billing cycle.