I'm looking to buy a used iPhone 5s from eBay. It will be used as an iPod Touch for a while, but I'll be moving out of the US in about a year or so. Sprint phones are by far the cheapest, but as I understand it, you have to be a Sprint customer for 3 months before they'll unlock it for international use (which is a condition I likely won't be fulfilling).
Would I be able to buy a bad ESN phone and use it abroad, then? It sounds like GSM phones are better for abroad use, but they're a bit more and I'm just trying to go down the cheapest route.
Thanks in advance!