If you're starting from scratch, do the math and see if it's worth it to use the upgrade (keep unlimited method) to buy an iPhone 5s and ebay/swappa or otherwise sell it and then buy the moto x outright with the proceeds, pocketing the difference. If it's not a huge win, move on... but it's something to consider.
Here's the math with the current Moto X code:
iPhone 5s is on sale at BestBuy for $150 + tax thru tomorrow. Use the upgrade to buy it. If you can get $550 by selling the iPhone after paypal, listing and shipping fees, that means you net $400 - tax for the iPhone.
Buy moto maker Moto X for $350 + tax with the current code. So depending on how much he can sell the iPhone 5s for and how much the tax is, he may make money off of the deal or at least break even, which is better than paying Verizon $100 + tax for the Moto X.
I didn't factor in the upgrade fee because if he used the upgrade to buy the Moto X from Verizon in the first place, he would pay the upgrade fee so the upgrade fee is a wash.
Please note that you can only do the transfer of the upgrade through Verizon, BestBuy or Costco without paying a secondary ETF when you switch the new phone onto your unlimited data line. Again, I refer you to the thread in the Verizon forum for detailed instructions on how to do this.