Your friend in the USA needs to pick up a compatible OBDII dongle (which one depends on which type of smartphone he uses) and purchase a software program such as LeafSpy. This is critical whenever buying a used Leaf, because unscrupulous dealers can (and have) reset the computer to make it look like the car has "all 12 bars." This eventually corrects itself, but often not until after you've had the car for a short time.
As mentioned earlier, the 2015 models are the "sweet spot" as they seem to have batteries that are the most resistant to premature degradation. Supposedly 2014 and later-built (after March 2013) 2013 models have decent batteries too. 2011/2012, and 2013 models built before April 2013, are only recommended if you know for a fact that the battery has been replaced, as Nissan uses the batteries included with the 2015's. Pre-2013 models lack significant upgrades of the later versions such as a more aggressive regen profile and a heater that uses less energy. 2011's I believe also lack seat and steering wheel heaters, or maybe only a few had them included; this became standard equipment starting in 2012.
I presume your friend also has a subscription to CarFax, but if not he needs to. One of the more useful aspects of CarFax is finding out where the car was purchased, and often where it has resided (based upon DMV and servicing history). As mentioned above, the Pacific Northwest (the area along the west coast of the US from the Canadian border south to far northern California; major cities are Seattle and Portland) has a very mild overall climate, not too cold in the winter and more importantly not too warm in summer. Leafs from this region tend to have the least battery degradation.
Note that all 2011 and 2012 models, and some 2013 and later models, use a slower (3.8 kW from the wall) on board charger; ones with the faster charger pull 6.6 kW from the wall. CHAdeMO fast charging was included in some trims, optional on others, and for pre-2013 cars was only included on the top trim SL (and not available at all on the lower trim SV).
Blue Ocean 2012 Leaf SV, lost that 1st bar at 34 months/26,435 miles. Lease returned 2 months later. Final LeafStat figures: 225 Gids, 17.44 kWH, SOC 91.89%, SOH 82.36%, 69.49% HX, 54.57 Ahr, battery temp 61.8 F.
Now driving a 2015 VW eGolf SEL.