Can I buy an Iphone 5c or 4s without a plan and just use it on Wi-Fi?

Is that possible or do i have to have a plan?

Yes you can use any phone like a prepaid

You can but it would be pointless and expensive. An unsubsidized iPhone will cost hundreds of dollars just to have what amounts to an iPod touch, and that would have cost far less.

No, you don't need a plan in order to use an iPhone with Wi-Fi only.

And the point would be? An iPhone is substantially more expensive than an iTouch when you buy it without a contract. Why would you spend the extra money?

No you don't