This question just popped up in our Galaxy Note 4 forums, but it's one that we've seen related to other phones before as well.
We're all so used to buying a phone with intentions of using it on a carrier that we often don't consider what it will operate like without a SIM in it. Rest assured that your phone will operate just fine without active service from a carrier, leaving it as a Wifi-only device.
Looking to order an unlocked [Galaxy Note 4] N910A off eBay. I'm moving in a couple of months, but where I live now I have no service at all so I'm wondering if I can use the phone's Wifi features in the mean time or do I need to activate it with a carrier before I can use any features at all?
Whether you're buying to use the phone on Wifi permanently or just for a short period of time — perhaps while you're traveling abroad — you won't find many issues. Great apps like Hangouts will even let you make VoIP calls without any carrier involvement, provided you're able to find good Wifi connections.
There are just a few things to be aware of when buying a phone to use without a carrier, though. Of course you're overpaying a bit for a device with cellular capabilities you aren't using, so consider weighing the difference in price between that unlocked phone and perhaps a small Wifi-only tablet. Also remember that phones use cellular connections to help with location information, so when you're out of the house without Wifi it's going to be a pain relying on just GPS with no data connection. And lastly, if you choose to buy a carrier-branded phone off-contract, you may run into issues getting software updates without an active SIM from that carrier in the phone.
That being said, picking up an unlocked phone to use just on Wifi can be a great solution if you're not ready to pay monthly for a phone plan or just want a second phone around for a specific use!