Need to decide on an iPhone that meets specific needs. Any suggestions?

I'm underage and living with my parents who don't want me getting a phone with a contract. I work and pay for all my belongings, so I'm trying to buy an unlocked iPhone. I was thinking I could get one, then buy prepaid minutes from those cards at stores as needed. Will this work? And where would I buy an iPhone like the one I need? It can be iPhone 5, 5s, 5c, 6, or 6 plus. (It needs to be an iPhone to support the apps I use)

If you're willing to spend $549 then you can get an iPhone 6 16Gb unlocked from Apple. The iPhone 5, and 5C are long discontinued, so you won't be able to buy one from Apple.

When you buy an unlocked phone, you get the phone, and you have to buy service from a carrier. How much it costs depends on the plan, but it may be as little as $30 to as high as $100 per month.