Just be sure to read everything before you sign it. The return policy will be in the paperwork you receive. Also, ask the rep that you talk to about their return policy. Standard is 14 days, with exception to California which is 30(others may have this as well). More than likely you will get pinged with a restocking fee, T-Mo corporate store's is a flat $10; others may be the same or a percentage as stated above.
Best of luck.