How much would it cost me to start a Sprint plan?

I just turned 18 last week and I want to start my own plan and buy an Iphone 5. I'm going to start the plan and since my mom has bad credit she and my little brother are going to join my plan. I was wondering how much it would cost all together to get started? I know I may have a deposit and I'm wondering how much it would be and if there was any hidden fees

My family (and our business) uses Sprint. I personally only pay $80/month for unlimited texting, data, and then 450 minutes. For three people, it shouldn't be too much. However, I'd recommend that you go into a Sprint store and check out plans for three people with whatever features you desire. Hope this was helpful