Iphone 6 and iphone 6plus was released September 19 in UK and USA before expanding to additional 56 countries on the 26th of September and middle of October..
Although alot of deal by some website have been online even before the released date.
Many people have been pretty tempted by these deals, but the concern most people raise is whether the phones are being sold legitimately, with a warranty.
There are 3 things you have to put into consideration.
First : You have to double check if the seller has a return policy.
Secondly : You should also check if the iPhone listing has the correct product model, and says the iPhone is new, and has a manufacturer warranty or dealer warranty – you want the former.
WHY THIS:
if there is any issue, you’ll be able to safely return the iPhone back to Apple without any problem.
Now for you to check In order to check if the iPhone is under warranty, there is one things you have to look for.
1. look up for the serial number of your iPhone. This should be listed on the box of the iPhone. If you don’t have the original packing with you, then i will advice you to follow the following steps:
1. Switch on the iPhone.
2. Go to Settings>General>About
Scroll down a little to check the Serial Number and copy this down safely.
3. Visit the Apple‘s site/Get Warranty and in the text box, enter the serial number of your iPhone , after that click on Continue.

Yes , After the above step , the warranty status of your iPhone will show up, as will the eligibility for extended coverage.
There are three headers: Purchase Date, Telephone Technical Support, and Repairs and Service Coverage.
If you bought a new iPhone, there should be a green tick mark next to all
3. If there isn’t, then the iPhone’s warranty has expired or wasn’t valid in the first place and My advice is that you should return the iPhone.
If it’s not a new phone, at the very least, you should see a green tick next to the “Repairs and Service Coverage” head, which indicates Apple will honor your request for repairs and service on your iPhone.

what do you think?.

SOURCE : Http://techcribng.com/iphone-warranty/

My experience is shown as below. If you still have some question, here is a guide to help you check the Warranty statue of iPhone.
Step 1. warranty check for iPhone will start from finding the serial number.
Step 2. This serial number can be found with iTunes, on the surface of smart phone or inside its firmware setting.
Step 3. Launch the Safari browser and then go-to this site.