If it's his only computer I would suggest a 12 -13" machine then. The 11" MacBook Air is probably a bit too small for a "primary machine".
IMO:
If budget is tight: MacBook Air 13" for $999 (128GB model).
This is an extremely compact machine with ample horsepower. The 128GB hard drive is small, but the onboard SDXC slot will allow him to double the onboard memory for stuff like photos and music via a
128GB SDXC Class 10 Card for $50. Also available in a 256GB model for an upcharge of $200 or so.
If you can swing it: MacBook Pro 13" with retina display for $1299 (128 GB model)
This is a measurably more potent machine overall, while still remaining very portable. Retina display, force touch touchpad, etc are all very current tech, while still retaining very good portability. This has the same ability to expand storage via SDXC slot, or you can splurge on the 256GB model if you'd like for an extra $200.
256GB Storage upgrade:
If money isn't a big issue, upgrading to 256GB storage is nice, as a 128GB hard drive is pretty limited (and the SDXC card is reasonably fast but not nearly as fast as the on-board hard drive). Unfortunately all computer manufacturers overprice this badly, Apple is among the worst. Difference between 128 and 256GB SSD is about $50-75 at retail.
Processor upgrades:
I wouldn't sweat the processor upgrades... I doubt he'd see much difference in real world use. Same goes with onboard RAM upgrades. WIth these machines being fully solid state with flash drives, the latency gap between HDD and RAM has narrowed immensely.
TIP:
If you're down to save more $$$, don't be afraid of
Apple's Refurbished machines section. I've heard very good things.