I finally purchased my first MacBook Pro so I can start iOS development. I do not own any iOS devices, other than my fiance's iPhone 4. I would like to ease myself into iOS development, so I am looking at purchasing a used iPhone 4. iPhone 4's can upgrade to iOS 6, so it seems to be the cheapest way to get into the iOS dev game.

Browsing ebay I see a lot of iPhones listed with bad ESN's. I understand this can mean it's a deactivated device which cannot be activated on a network, but would such a device be able to suffice my needs as a introductory development platform for either PhoneGap or native app development?

Would there be any pitfalls that may prevent me from working on wifi? I would not be activating the device on Sprint or anything, so could I theoretically buy some cheap att or verizon iPhone with a bad ESN and just use it on my local wifi for development purposes?