For something different than his .270 Win., for plinking, target shooting, even maybe some long range target work, and economical for ammo or loading components, the answer has to be the .223 Rem. A Howa, Ruger American, Savage, or Marlin bolt action would fit his budget and provide excellent accuracy and reliability, or if he ups his budget and decides to to go AR, the new Ruger AR556 might be the ticket, with its' 1 in 8" twist to handle the heavier bullets for long range shooting. Ammo can be found for as lttle as .33 per round, or less than half of what you pay for basic .270 Win ammo. He can save up his brass for both and eventually invest in reloading equipment and be able to shoot both cartridges much more economically. (especially now that powder and primers are once again available at more reasonable prices)
Of course, he should have a .22 rimfire or 2 or 3, but if he is talking centerfire, and his .270 Win handles all his medium/big game hunting activities, it sure sounds like a rifle chambered in .223 Remington is what might prove his best option.