If he has T-Mobile, he can get a Hotspot account, which let's him surf via wi-fi at any wi-fi enabled area (home, Starbucks, Barnes & Nobles, Airports, train stations, etc.). The cost is something like 10 buck extra per month. Outside of Hotspot locations, he would then just surf over the cell phone network.
As for other carriers, I don't know their rate plans.
Either way, he will need a wireless card for the laptop (some newer laptops have them built in). The card is cheap or free these days.
Hope that helps!