Both Verizon and Sprint have deals right now where if you buy one of the iPhone X smartphones (including the XR, X, XS, or XS Max), you can get a second new iPhone XR for free. It's a great deal but each one varies slightly, which might help you choose which carrier to go with.
The Sprint deal requires either two new lines or one new and one upgraded line. You will sign up for an 18-month lease, and you will need approved credit. If you don't need two smartphones, Sprint has an ongoing deal we reported back in April where you can get just the iPhone XR on the Flex Lease for $15 a month instead of its regular $31.25 a month. Unfortunately, you probably won't be able to stack the two deals.
Verizon's sale actually includes a $750 promo credit that's applied to your account over a 24-month period. That means for this one it doesn't necessarily have to be an iPhone XR for your second phone. You'll just save as much as $750 even if you choose to go with the $1,100 XS Max. Just add the second phone to a new line of service on the Unlimited plan. Of course, this lease is six months longer than Sprint's, and Sprint has the iPhone Forever program that lets you upgrade to the newest iPhone anytime after 12 lease payments.
The iPhone XR is available at this price in several colors including Black, White, Yellow, Coral, Blue, and Apple's (Product)Red. Some of the colors are limited in stock at different storage capacities.
Check out our review of the iPhone XR where we gave it 4.5 stars out of 5 and said "It has almost everything you'd want in a flagship phone for 2018, minus the price tag that's typically coming with them these days." Our reviewer even used the phone for a month and wrote a followup afterward where he said "iPhone XR is legit a great product and it's going to be a great phone choice for a lot of people."
We also took a look at the iPhone XS seven months after its release. Renee Ritchie said "...if you need it or would benefit from getting it now, absolutely get an iPhone XS — or XR if you don't care about the OLED display or dual camera system and want to save some cash — now and have zero regrets." The review adds the "iPhone X was all new. iPhone XS is just all better. Better camera, better battery, better Face ID, better performance, and a new gold option. More than just being a great user experience, 7-months later something else is clear as well: It's a phone you can rely on."