Thanks. Although I don't believe you need to purchase outright unless you want to unlock domestically. No mention of having to have it paid in full under international unlock but certainly states must be paid off for domestic unlock.
Per Sprint's Website:
Unlocking for international travel
Traveling abroad? Sprint customers traveling abroad for a short period of time may be eligible to have their Sprint service provisioned to allow for international roaming. See sprint.com/international for full details.
Current Sprint customers remaining abroad for an extended period of time may want to try to use their Sprint device with a foreign carrier. As a courtesy for our customers, for certain devices, Sprint may be able to unlock the device SIM slot for a foreign carrier's SIM card to be inserted. Customers must meet the following conditions to be eligible:
-The device is capable of international SIM unlock
-The person requesting the international SIM unlock is a current Sprint customer that can authenticate as the Account Holder or an Authorized Contact
-The applicable device is currently active on a Sprint account and the applicable account has been active for at least 90 days.
-The account is in good standing
-Each phone number on the account is allowed up to two unlocked devices within a 12 month period.
T-he device has not been reported as lost or stolen, associated with fraudulent activity, or otherwise flagged as ineligible to be unlocked